Backport of "splitmuxsink: Only set running time on finalizing sink element when in async-finalize mode" into 1.16
Backport of !210 (merged) "splitmuxsink: Only set running time on finalizing sink element when in async-finalize mode".
Commits:
- 32c465a5 splitmuxsink: Only set running time on finalizing sink element when in async-finalize mode