If during shutdown the pacer has packets enqueued during pause these
packets will be posted to the pacer after the worker thread is free -
after the ssrcs should have been cleared. This fixes flakes in
picutre_id_tests.
Bug: webrtc:14985
Change-Id: Ib5547a501670fc145543df32fdc43bbc6596375f
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/297401
Reviewed-by: Per Kjellander <perkj@webrtc.org>
Reviewed-by: Erik Språng <sprang@webrtc.org>
Commit-Queue: Evan Shrubsole <eshr@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#39640}
a7b691499b