tools/qvm-start-gui: avoid starting a VM just to send it monitor layout

If the VM is powered off shortly after startup, it may happen that
qubes.SetMonitorLayout would start it again. Avoid this by using
autostart=False argument to run_service() function.

Note that there is a vm.is_running() check at the beginning of the
function already, but if it happens while the VM is cleaned up, it may
still report that it's running, but at the time of run_service() call it
is not.

qubesadmin/tests/tools/qvm_start_gui.py

@@ -511,7 +511,7 @@ HDMI1 connected 2560x1920+0+0 (normal left inverted right x axis y axis) 206mm x
         loop.run_until_complete(self.launcher.send_monitor_layout(
             vm, layout=monitor_layout, startup=True))
         mock_run_service.assert_called_once_with(
-            'qubes.SetMonitorLayout', b'1920 1080 0 0\n')
+            'qubes.SetMonitorLayout', autostart=False, input=b'1920 1080 0 0\n')
         self.assertAllCalled()
 
     def test_061_send_monitor_layout_exclude(self):

qubesadmin/tools/qvm_start_gui.py

@@ -25,6 +25,8 @@ import signal
 import subprocess
 import asyncio
 import re
+
+import functools
 import xcffib
 import xcffib.xproto  # pylint: disable=unused-import
 
@@ -292,8 +294,10 @@ class GUILauncher(object):
 
         try:
             yield from asyncio.get_event_loop().run_in_executor(None,
-                vm.run_service_for_stdio, 'qubes.SetMonitorLayout',
-                    ''.join(layout).encode())
+                functools.partial(vm.run_service_for_stdio,
+                                  'qubes.SetMonitorLayout',
+                                  input=''.join(layout).encode(),
+                                  autostart=False))
         except subprocess.CalledProcessError as e:
             vm.log.warning('Failed to send monitor layout: %s', e.stderr)