audio: Don't update the audio_output flag with track flags

 Use the AUDIO_OUTPUT_FLAG_DIRECT only for creating
 the track and do not add this in the audio_flags
 of AudioTrack, as adding this to audio_flags of
 AudioTrack is not expected and lead to side effects.

Change-Id: Ic85ad5aef91e147a209d1c7a3a7ef0728f3d4207