Backport of "rtprawdepay: Don't get rid of the buffer pool on FLUSH_STOP" into 1.16
Backport of !197 (merged) "rtprawdepay: Don't get rid of the buffer pool on FLUSH_STOP".
Commits:
- c4608b41 rtprawdepay: Don't get rid of the buffer pool on FLUSH_STOP