Backport of "rtpbin: Avoid holding GST_RTP_BIN_LOCK when emitting pad-added" into 1.20
Backport of !2411 (merged) "rtpbin: Avoid holding GST_RTP_BIN_LOCK when emitting pad-added".
Commits:
- 1cb4c050 rtpbin: Avoid holding lock GST_RTP_BIN_LOCK when emitting pad-added