MAVLink app: Fix boot-time race between receive thread and instantiation.

src/modules/mavlink/mavlink_main.cpp

@@ -1988,9 +1988,6 @@ Mavlink::task_main(int argc, char *argv[])
 	/* Initialize system properties */
 	mavlink_update_system();
 
-	/* start the MAVLink receiver */
-	MavlinkReceiver::receive_start(&_receive_thread, this);
-
 	MavlinkOrbSubscription *param_sub = add_orb_subscription(ORB_ID(parameter_update));
 	uint64_t param_time = 0;
 	MavlinkOrbSubscription *status_sub = add_orb_subscription(ORB_ID(vehicle_status));
@@ -2180,6 +2177,9 @@ Mavlink::task_main(int argc, char *argv[])
 		send_autopilot_capabilites();
 	}
 
+	/* start the MAVLink receiver last to avoid a race */
+	MavlinkReceiver::receive_start(&_receive_thread, this);
+
 	while (!_task_should_exit) {
 		/* main loop */
 		usleep(_main_loop_delay);