Hi,
I just realized that QEMU Guest Agent is part of standard QEMU package, and it is already on unRAID. Just add following line before "/usr/local/sbin/emhttp &" in /boot/config/go file:
/usr/bin/qemu-ga -l /var/log/qemu-ga.log -d
You can try running it directly in terminal, just be sure that QEMU Guest Agent is enabled in Options on VM Options section.
Best regards,
Maciej