Fix starting audio daemon

After QubesOS/qubes-core-admin#689 the type of
the 'xid' property is preserved and it's int now. Fix pacat daemon
parameters to convert it back to string.

Author: marmarek

qubesadmin/tools/qvm_start_daemon.py

@@ -665,7 +665,12 @@ async def start_audio_for_vm(self, vm):
 
         :param vm: VM for which start AUDIO daemon
         """
-        pacat_cmd = [PACAT_DAEMON_PATH, '-l', self.pacat_domid(vm), vm.name]
+        pacat_cmd = [
+            PACAT_DAEMON_PATH,
+            "-l",
+            str(self.pacat_domid(vm)),
+            vm.name,
+        ]
         vm.log.info('Starting AUDIO')
 
         await asyncio.create_subprocess_exec(*pacat_cmd)