Fixed mavlink start / stop to ensure process is in a sane state once NSH return

src/modules/mavlink/mavlink.c

@@ -743,7 +743,7 @@ int mavlink_thread_main(int argc, char *argv[])
 
 	thread_running = false;
 
-	exit(0);
+	return 0;
 }
 
 static void
@@ -767,7 +767,7 @@ int mavlink_main(int argc, char *argv[])
 
 		/* this is not an error */
 		if (thread_running)
-			errx(0, "mavlink already running\n");
+			errx(0, "mavlink already running");
 
 		thread_should_exit = false;
 		mavlink_task = task_spawn_cmd("mavlink",
@@ -776,15 +776,25 @@ int mavlink_main(int argc, char *argv[])
 					  2048,
 					  mavlink_thread_main,
 					  (const char **)argv);
+
+		while (!thread_running) {
+			usleep(200);
+		}
+
 		exit(0);
 	}
 
 	if (!strcmp(argv[1], "stop")) {
+
+		/* this is not an error */
+		if (!thread_running)
+			errx(0, "mavlink already stopped");
+
 		thread_should_exit = true;
 
 		while (thread_running) {
 			usleep(200000);
-			printf(".");
+			warnx(".");
 		}
 
 		warnx("terminated.");