Do not set SamplingRate for DirectTrack

- Setting sampling rate on DirectOutput track
  is failing in MediaPlayer.cpp when opening
  AudioOutput. Audiotrack does not allow to
  set SamplingRate for DirectOutputTrack.

- Fix is to check AudioOutput type in Media
  PlayerService and restrict setting Sampli
  ngRate if Output type is DirectOutput

Change-Id: I55fbc58cef299ca757f850c266ccca602b0e5888