parameters: lock shutdown earlier in param_save_default()

- this ensures the parameter file is closed properly before shutdown

src/lib/parameters/parameters.cpp

@@ -949,8 +949,7 @@ param_get_default_file()
 	return (param_user_file != nullptr) ? param_user_file : param_default_file;
 }
 
-int
+int param_save_default()
-param_save_default()
 {
 	int res = PX4_ERROR;
 
@@ -965,11 +964,22 @@ param_save_default()
 		return res;
 	}
 
+	int shutdown_lock_ret = px4_shutdown_lock();
+
+	if (shutdown_lock_ret) {
+		PX4_ERR("px4_shutdown_lock() failed (%i)", shutdown_lock_ret);
+	}
+
 	/* write parameters to temp file */
 	int fd = PARAM_OPEN(filename, O_WRONLY | O_CREAT, PX4_O_MODE_666);
 
 	if (fd < 0) {
 		PX4_ERR("failed to open param file: %s", filename);
+
+		if (shutdown_lock_ret == 0) {
+			px4_shutdown_unlock();
+		}
+
 		return PX4_ERROR;
 	}
 
@@ -991,6 +1001,10 @@ param_save_default()
 
 	PARAM_CLOSE(fd);
 
+	if (shutdown_lock_ret == 0) {
+		px4_shutdown_unlock();
+	}
+
 	return res;
 }