"Guest says index 40947 is available"
Description of problem:
As discussed [here](https://github.com/danobi/vmtest/issues/96) I have been running several instances of QEMU in parallel at `SCHED_IDLE`, and I've been getting QGA setup failures.
Steps to reproduce:
1. Install [vmtest](https://github.com/danobi/vmtest)
2. Run lots of copies of the command in the [github issues](https://github.com/danobi/vmtest/issues/96) via `chrt --idle 0`.
3. Unclear if this is the cause, but then I use the computer in the meantime so probably starve the `SCHED_IDLE` QEMU threads running from 2.

This leads to failures to connect to the guest agent and then at the end I see this:

```
Guest says index 40947 is available
    qemu-system-x86_64: Guest says index 40947 is available
    qemu-system-x86_64: Guest says index 40947 is available
```


The developer of vmtest seemed to think this may be of interest to QEMU developers based on the tone of the [comment they found](https://github.com/danobi/vmtest/issues/96#issuecomment-2483860554) in the QEMU code.

I've now installed QEMU from Git master so I can report back whether the bug still appeared.