Merge pull request #788 from PX4/mavlink_published_fix

mavlink: is_published() fix

src/modules/mavlink/mavlink_orb_subscription.cpp

@@ -88,6 +88,7 @@ MavlinkOrbSubscription::update(const hrt_abstime t)
 
 		if (_updated) {
 			orb_copy(_topic, _fd, _data);
+			_published = true;
 			return true;
 		}
 	}