[dvdplayer] Fix for timestamp correction when no audio or no video

If audio or video track is missing, we don't have to wait for the other track to have a matching timestamp jump
Also compare dts rather than correction values as suggested by FernetMenta

This aims to fix a bug in https://github.com/xbmc/xbmc/pull/5248 identified by @ace20022.
@FernetMenta does the additional commit help?