dbusService: Queue shutdown check on startup

If something started the service, but crashed before managing to make a
method call, we'd end up with the service running indefinitely. Fix this
by queueing a shutdown check immediately on startup.

https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1372

js/dbusServices/dbusService.js

@@ -25,6 +25,8 @@ var ServiceImplementation = class {
 
         // subclasses may override this to disable automatic shutdown
         this._autoShutdown = true;
+
+        this._queueShutdownCheck();
     }
 
     // subclasses may override this to own additional names