Fix gui-daemon cleanup

The cleanup requires XID of the domain, but when it's shut off already,
it's too late to retrieve it. Cache value retrieved when the domain was
still running (either domain-start event, or program startup).

qubesadmin/tools/qvm_start_daemon.py

@@ -326,6 +326,10 @@ class DAEMONLauncher:
         self.vm_names = vm_names
         self.kde = kde
 
+        # cache XID values when the VM was still running -
+        # for cleanup purpose
+        self.xid_cache = {}
+
     async def send_monitor_layout(self, vm, layout=None, startup=False):
         """Send monitor layout to a given VM
 
@@ -607,6 +611,8 @@ class DAEMONLauncher:
         if not self.is_watched(vm):
             return
 
+        self.xid_cache[vm.name] = vm.xid, vm.stubdom_xid
+
         try:
             if getattr(vm, 'guivm', None) == vm.app.local_name and \
                     vm.features.check_with_template('gui', True) and \
@@ -641,6 +647,7 @@ class DAEMONLauncher:
                 asyncio.ensure_future(
                     self.start_gui(vm, monitor_layout=monitor_layout))
                 asyncio.ensure_future(self.start_audio(vm))
+                self.xid_cache[vm.name] = vm.xid, vm.stubdom_xid
             elif power_state == 'Transient':
                 # it is still starting, we'll get 'domain-start'
                 # event when fully started
@@ -654,9 +661,16 @@ class DAEMONLauncher:
         if not self.is_watched(vm):
             return
 
-        self.cleanup_guid(vm.xid)
-        if vm.virt_mode == 'hvm':
-            self.cleanup_guid(vm.stubdom_xid)
+        # read XID from cache, as stopped domain reports it already as -1
+        try:
+            xid, stubdom_xid = self.xid_cache[vm.name]
+            del self.xid_cache[vm.name]
+        except KeyError:
+            return
+        if xid != -1:
+            self.cleanup_guid(xid)
+        if stubdom_xid != -1:
+            self.cleanup_guid(stubdom_xid)
 
     def cleanup_guid(self, xid):
         """