Backport of "qtdemux: Don't emit GstSegment correcting start time when in MSE mode" into 1.22
Backport of !3867 (merged) "qtdemux: Don't emit GstSegment correcting start time when in MSE mode".
Commits:
- 92a4cfe2 qtdemux: Don't emit GstSegment correcting start time when in MSE mode