Backport of "avauddec/avviddec: Avoid dropping non-OK flow return" into 1.18
Backport of !90 (merged) "avauddec/avviddec: Avoid dropping non-OK flow return".
Commits:
- c6e51f40 avauddec: Avoid dropping non-OK flow return
- 90a079cc avviddec: Forward flow returns from draining instead of assuming OK
- 6ea6f154 avauddec: Forward flow returns from draining instead of assuming OK
- 7388b144 avauddec: Ensure finish_subframe() and finish_frame() are paired
- 72933810 avviddec: Don't return GST_FLOW_EOS from drain()/finish()