virtio-scsi in Windows guests cause QEMU to abort/crash
Description of problem:
* Attempting to load the virtio-scsi drivers in a Windows guest causes the VM to abort/crash.
Steps to reproduce:
* `qemu-system-x86_64 -accel kvm -m 4G -device virtio-scsi-pci,id=scsi0 -drive media=cdrom,file=windows7-x64.iso -drive media=cdrom,file=virtio-win-0.1.173.iso`
 * Boot the installer ISO, click through all the menus to eventually get to Custom Install
 * In "Where do you want to install" click Load driver
 * Browse E: drive and pick the first amd64/w7 folder
 * Should show "Red Had VirtIO SCSI pass-through controller"
 * Click Next
 * Abort/crash

Same thing happens with VM's that used to work already running the virtio-scsi drivers. When they boot the VM aborts.
Additional information:
```
qemu-system-x86_64: ../accel/kvm/kvm-all.c:1760: kvm_irqchip_commit_routes: Assertion `ret == 0' failed.
Aborted (core dumped)
```