Protect writer stop jobs from competing healthcheck requests

tests/test_backup.py

@@ -494,7 +494,8 @@ if '--list-only' not in sys.argv and '--exclude=/*' not in sys.argv and '--dry-r
         self.assertNotIn('systemctl stop',self.events.read_text())
 
     def test_service_stop_and_start_failures_are_reported(self):
-        self.run_script('app-backup.sh',ok=False,TEST_FAIL_SERVICE='stop:gitea')
+        result=self.run_script('app-backup.sh',ok=False,TEST_FAIL_SERVICE='stop:gitea')
+        self.assertIn('Could not stop writer gitea',result.stdout)
         self.assertEqual(json.loads(self.state.read_text()),self.initial)
         self.run_script('app-backup.sh',ok=False,TEST_FAIL_SERVICE='start:gitea')
         self.assertTrue(list((self.base/'work').glob('recovery-*.json')))