Backport of "rtspconnection: protect cancellable by a mutex" into 1.20
requested to merge tpm/gstreamer:backport-mr-2799-into-1.20-rtspconnection-cancellable-lock into 1.20
Backport of !2799 (merged) "rtspconnection: protect cancellable by a mutex".
Commits:
- 598f2ab7 rtspconnection: protect cancellable by a mutex