Add generic support for mpd manifests(dash formats)
For consistency between python 2 and 3.
Broken since a6c2c24479. Thanks to @jaimeMF and @anisse for pointing that out
a6c2c24479
[ffmpeg] fix adding metadata when using m3u8_native(fixes #8350)
[utils] fix dfxp2srt text extraction(fixes #8055)
Facebook DASH formats