Hotfix: Close fd before reusing it again

src/modules/commander/state_machine_helper.cpp

@@ -666,6 +666,8 @@ int prearm_check(const struct vehicle_status_s *status, const int mavlink_fd)
 	}
 
 	if (!status->is_rotary_wing) {
+		/* accel done, close it */
+		close(fd);
 		fd = open(AIRSPEED_DEVICE_PATH, O_RDONLY);
 
 		if (fd < 0) {