Fix for multiple audio/timed track feature implementation - part one

o getTrackInfo now returns all tracks, rather than just the timed text tracks.
o the index of the track info is kept to the same as the track index if the
  track is not from an external source
o correctly maps the selectTrack() and unselectTrack() calls to the right
  track index

o TODO:
  1) note that the selectTrack() and unselectTrack() only works for timed text
  track at present; 2) the lock is timed text specific

o related-to-bug: 6110705

Change-Id: Ib1feeef2184bc992930ace0d1197b6c00a2636d7