virtio-net: memory leak when hotplugging virtio-net
Description of problem:
When invalid option for virtio-net device is provided during hotplug, allocated string is not freed, leading to memory leak.
Steps to reproduce:
```sh
cat <<EOF | qemu-system-i386 -M q35 -nodefaults \
-chardev stdio,id=char0 -mon char0 -device pcie-pci-bridge,id=br1,bus=pcie.0
device_add virtio-net,rx_queue_size=0,bus=br1,id=dev0
quit
EOF
```

If above command is not working, let me know so that I provide more information.
Additional information:
There is LeakSanitizer log:

```sh
$ cat <<EOF | LSAN_OPTIONS=fast_unwind_on_malloc=0 qemu-system-i386 -M q35 -nodefaults \
-chardev stdio,id=char0 -mon char0 -device pcie-pci-bridge,id=br1,bus=pcie.0
device_add virtio-net,rx_queue_size=0,bus=br1,id=dev0
quit
EOF
==831633==WARNING: ASan doesn't fully support makecontext/swapcontext functions and may produce false positives in some cases!
QEMU 8.1.93 monitor - type 'help' for more information
VNC server running on 127.0.0.1:5900
(qemu) device_add virtio-net,rx_queue_size=0,bus=br1,id=dev0
Error: Invalid rx_queue_size (= 0), must be a power of 2 between 256 and 1024.
(qemu) quit

=================================================================
==831633==ERROR: LeakSanitizer: detected memory leaks

Direct leak of 15 byte(s) in 1 object(s) allocated from:
    #0 0x55c1ac66b3ce in malloc (/usr/local/bin/qemu-system-i386+0x1b5d3ce) (BuildId: c7ca543ea41d3478bc13cdf604d47805b990620e)
    #1 0x7f45c1695738 in g_malloc (/lib/x86_64-linux-gnu/libglib-2.0.so.0+0x5e738) (BuildId: 224ac2a88b72bc8e2fe8566ee28fae789fc69241)
    #2 0x7f45c16aa583 in g_strdup (/lib/x86_64-linux-gnu/libglib-2.0.so.0+0x73583) (BuildId: 224ac2a88b72bc8e2fe8566ee28fae789fc69241)
    #3 0x55c1ad943dd4 in virtio_net_set_netclient_name /home/XXX/qemu/build/../hw/net/virtio-net.c:3445:25
    #4 0x55c1adace541 in virtio_net_pci_realize /home/XXX/qemu/build/../hw/virtio/virtio-net-pci.c:62:5
    #5 0x55c1ad13ec00 in virtio_pci_realize /home/XXX/qemu/build/../hw/virtio/virtio-pci.c:2228:9
    #6 0x55c1acdec557 in pci_qdev_realize /home/XXX/qemu/build/../hw/pci/pci.c:2117:9
    #7 0x55c1adcb9484 in device_set_realized /home/XXX/qemu/build/../hw/core/qdev.c:510:13
    #8 0x55c1adcd6278 in property_set_bool /home/XXX/qemu/build/../qom/object.c:2305:5
    #9 0x55c1adcd1443 in object_property_set /home/XXX/qemu/build/../qom/object.c:1435:5
    #10 0x55c1adcdd15c in object_property_set_qobject /home/XXX/qemu/build/../qom/qom-qobject.c:28:10
    #11 0x55c1adcd1d11 in object_property_set_bool /home/XXX/qemu/build/../qom/object.c:1504:15
    #12 0x55c1ad27021a in qdev_device_add_from_qdict /home/XXX/qemu/build/../system/qdev-monitor.c:719:10
    #13 0x55c1ad271364 in qdev_device_add /home/XXX/qemu/build/../system/qdev-monitor.c:738:11
    #14 0x55c1ad2726eb in qmp_device_add /home/XXX/qemu/build/../system/qdev-monitor.c:860:11
    #15 0x55c1ad27311d in hmp_device_add /home/XXX/qemu/build/../system/qdev-monitor.c:968:5
    #16 0x55c1ad3bfef4 in handle_hmp_command_exec /home/XXX/qemu/build/../monitor/hmp.c:1106:9
    #17 0x55c1ad3bdfa3 in handle_hmp_command /home/XXX/qemu/build/../monitor/hmp.c:1158:9
    #18 0x55c1ad3b99ee in monitor_command_cb /home/XXX/qemu/build/../monitor/hmp.c:47:5
    #19 0x55c1ae3d5c3a in readline_handle_byte /home/XXX/qemu/build/../util/readline.c:419:13
    #20 0x55c1ad3c2261 in monitor_read /home/XXX/qemu/build/../monitor/hmp.c:1390:13
    #21 0x55c1ae0ff644 in fd_chr_read /home/XXX/qemu/build/../chardev/char-fd.c:72:9
    #22 0x7f45c168cc43 in g_main_context_dispatch (/lib/x86_64-linux-gnu/libglib-2.0.so.0+0x55c43) (BuildId: 224ac2a88b72bc8e2fe8566ee28fae789fc69241)
    #23 0x55c1ae3786db in glib_pollfds_poll /home/XXX/qemu/build/../util/main-loop.c:290:9
    #24 0x55c1ae3786db in os_host_main_loop_wait /home/XXX/qemu/build/../util/main-loop.c:313:5
    #25 0x55c1ae3786db in main_loop_wait /home/XXX/qemu/build/../util/main-loop.c:592:11
    #26 0x55c1ad282d06 in qemu_main_loop /home/XXX/qemu/build/../system/runstate.c:782:9
    #27 0x55c1adca6115 in qemu_default_main /home/XXX/qemu/build/../system/main.c:37:14
    #28 0x7f45c0bd0d8f in __libc_start_call_main csu/../sysdeps/nptl/libc_start_call_main.h:58:16
    #29 0x7f45c0bd0e3f in __libc_start_main csu/../csu/libc-start.c:392:3

Direct leak of 5 byte(s) in 1 object(s) allocated from:
    #0 0x55c1ac66b3ce in malloc (/usr/local/bin/qemu-system-i386+0x1b5d3ce) (BuildId: c7ca543ea41d3478bc13cdf604d47805b990620e)
    #1 0x7f45c1695738 in g_malloc (/lib/x86_64-linux-gnu/libglib-2.0.so.0+0x5e738) (BuildId: 224ac2a88b72bc8e2fe8566ee28fae789fc69241)
    #2 0x7f45c16aa583 in g_strdup (/lib/x86_64-linux-gnu/libglib-2.0.so.0+0x73583) (BuildId: 224ac2a88b72bc8e2fe8566ee28fae789fc69241)
    #3 0x55c1ad943da2 in virtio_net_set_netclient_name /home/XXX/qemu/build/../hw/net/virtio-net.c:3444:25
    #4 0x55c1adace541 in virtio_net_pci_realize /home/XXX/qemu/build/../hw/virtio/virtio-net-pci.c:62:5
    #5 0x55c1ad13ec00 in virtio_pci_realize /home/XXX/qemu/build/../hw/virtio/virtio-pci.c:2228:9
    #6 0x55c1acdec557 in pci_qdev_realize /home/XXX/qemu/build/../hw/pci/pci.c:2117:9
    #7 0x55c1adcb9484 in device_set_realized /home/XXX/qemu/build/../hw/core/qdev.c:510:13
    #8 0x55c1adcd6278 in property_set_bool /home/XXX/qemu/build/../qom/object.c:2305:5
    #9 0x55c1adcd1443 in object_property_set /home/XXX/qemu/build/../qom/object.c:1435:5
    #10 0x55c1adcdd15c in object_property_set_qobject /home/XXX/qemu/build/../qom/qom-qobject.c:28:10
    #11 0x55c1adcd1d11 in object_property_set_bool /home/XXX/qemu/build/../qom/object.c:1504:15
    #12 0x55c1ad27021a in qdev_device_add_from_qdict /home/XXX/qemu/build/../system/qdev-monitor.c:719:10
    #13 0x55c1ad271364 in qdev_device_add /home/XXX/qemu/build/../system/qdev-monitor.c:738:11
    #14 0x55c1ad2726eb in qmp_device_add /home/XXX/qemu/build/../system/qdev-monitor.c:860:11
    #15 0x55c1ad27311d in hmp_device_add /home/XXX/qemu/build/../system/qdev-monitor.c:968:5
    #16 0x55c1ad3bfef4 in handle_hmp_command_exec /home/XXX/qemu/build/../monitor/hmp.c:1106:9
    #17 0x55c1ad3bdfa3 in handle_hmp_command /home/XXX/qemu/build/../monitor/hmp.c:1158:9
    #18 0x55c1ad3b99ee in monitor_command_cb /home/XXX/qemu/build/../monitor/hmp.c:47:5
    #19 0x55c1ae3d5c3a in readline_handle_byte /home/XXX/qemu/build/../util/readline.c:419:13
    #20 0x55c1ad3c2261 in monitor_read /home/XXX/qemu/build/../monitor/hmp.c:1390:13
    #21 0x55c1ae0ff644 in fd_chr_read /home/XXX/qemu/build/../chardev/char-fd.c:72:9
    #22 0x7f45c168cc43 in g_main_context_dispatch (/lib/x86_64-linux-gnu/libglib-2.0.so.0+0x55c43) (BuildId: 224ac2a88b72bc8e2fe8566ee28fae789fc69241)
    #23 0x55c1ae3786db in glib_pollfds_poll /home/XXX/qemu/build/../util/main-loop.c:290:9
    #24 0x55c1ae3786db in os_host_main_loop_wait /home/XXX/qemu/build/../util/main-loop.c:313:5
    #25 0x55c1ae3786db in main_loop_wait /home/XXX/qemu/build/../util/main-loop.c:592:11
    #26 0x55c1ad282d06 in qemu_main_loop /home/XXX/qemu/build/../system/runstate.c:782:9
    #27 0x55c1adca6115 in qemu_default_main /home/XXX/qemu/build/../system/main.c:37:14
    #28 0x7f45c0bd0d8f in __libc_start_call_main csu/../sysdeps/nptl/libc_start_call_main.h:58:16
    #29 0x7f45c0bd0e3f in __libc_start_main csu/../csu/libc-start.c:392:3

SUMMARY: AddressSanitizer: 20 byte(s) leaked in 2 allocation(s).
```

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