mythburn.py: pass the starttime in utc format to mythtranscode

I can't easily test this but hopefully this will fix the problems reported on
the user mailing list and in #11758.

Refs #11758.

Signed-off-by: Paul Harrison <pharrison@mythtv.org>
MythMusic: add support for embedded images in flac xiphComment tags

Refs #11947.

Signed-off-by: Paul Harrison <pharrison@mythtv.org>
MythMusic: prefer xiphComment style tags in flac files

Closes #11947.

Signed-off-by: Paul Harrison <pharrison@mythtv.org>
Merge remote-tracking branch 'upstream/master'