Wait for PS to start again to fix race issues with activation

shell/session/Session.py

@@ -54,6 +54,12 @@ class Session:
 		process.start()
 
 		PresenceService.start()
+		bus = dbus.Bus()
+		ret = False
+		# Wait for the presence service to start up before continuing
+		while not ret:
+			ret = dbus.dbus_bindings.bus_name_has_owner(bus._connection, PresenceService.DBUS_SERVICE)
+			time.sleep(0.2)
 
 		process = MatchboxProcess()
 		process.start()