Backport of "mpegtsmux: Start last_ts with GST_CLOCK_TIME_NONE" into 1.20
Backport of !1884 (merged) "mpegtsmux: Start last_ts with GST_CLOCK_TIME_NONE".
Commits:
Backport of !1884 (merged) "mpegtsmux: Start last_ts with GST_CLOCK_TIME_NONE".
Commits: