Backport of "rtsp-stream: use mcast_udpsink[0] last-sample if available for rtpinfo" into 1.16
Backport of !112 (merged) "rtsp-stream: use mcast_udpsink[0] last-sample if available for rtpinfo".
Commits:
- a696d980 rtsp-stream: use mcast_udpsink[0] last-sample if available for rtpinfo