python3-mb: old jack.toc files may list data tracks

[pimzand]

Old jack.toc files may list data tracks. Using these toc files in libdiscid to query MusicBrainz will not return valid releases.

[pimzand]

To make it worse, data tracks are listed as audio tracks in jack.toc. But I now found out that they are marked as data tracks in jack.progress, with lines like these:

11/|\off/|\non-audio

This could be used to filter out these tracks when recalculating the discid

[pimzand]

Since commit c6c8c4e, we now detect toc files containing data tracks, created using older versions of Jack that used CDDB.py. This could still work for freedb/gnudb queries, but never for MusicBrainz.

Ideally, we could just remove the datatracks from the query, but it turns out that CDDB.py, when handling discs with data tracks, gets the length of the last audio track wrong, removing an any chance for a successful MusicBrainz query.