Comment 30 for bug 1552241

Is fixed in Ubuntu 17.10 with latest patches.

I've upgraded my ubuntu desktop 17.10 machine and the apparmor file was indeed patched; I shut down my Windows VM, reloaded apparmor and restarted libvirtd, and it was able to pass through the USB audio device.

Aside: I use xfreerdp to connect to the machine and use the flag "/audio-mode:1" ; this causes the Windows VM to use local audio, and this is how I am able to use the Cisco Jabber VOIP application with the USB headset.