virt-aa-helper missing host devices when restoring saved VM

[Paul Donohue]

Example:
* Add a host device to a VM:
   <hostdev mode='subsystem' type='usb'>
     <source startupPolicy='optional'>
       <vendor id='0x1234'/>
       <product id='0x1234'/>
     </source>
   </hostdev>
* Start the VM and confirm that virt-aa-helper has added the associated /dev/bus/usb/... path to /etc/apparmor.d/libvirt/libvirt-<UUID>.files
* Save the VM by clicking "Shut Down" -> "Save" in virt-manager.
* Restore the VM by clicking "Restore" in virt-manager.
* virt-manager displays a qemu "permission denied" error message for the /dev/bus/usb/... file associated with the host device that was attached to the VM.

Running `while true ; cat /etc/apparmor.d/libvirt/libvirt-<UUID>.files 2>/dev/null ; done` when restoring the VM shows that virt-aa-helper is generating an apparmor policy but is not including the relevant /dev/bus/usb/... path in the generated policy.