create transport master in the factory method if the engine is running

This fixes the GUI thinking there is no port because it is notified about the TM before the port
is created

libs/ardour/transport_master.cc

@@ -401,6 +401,9 @@ TransportMaster::factory (SyncSource type, std::string const& name, bool removea
 	}
 
 	if (tm) {
+		if (AudioEngine::instance()->running()) {
+			tm->create_port ();
+		}
 		tm->set_removeable (removeable);
 	}