avformat/movenc: Move avid DNxHD padding to the correct spot

Outputting DNxHD into .mov containers 'corrupts' following atoms until end of stsd

ffmpeg and qtdump could not decode pasp/colr atoms in the files made by ffmpeg,
when outputting DNxHD due to the incorrect padding placement. Now we add the
padding in the correct place

Tidy up FATE changes due to padding changes.

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
