stagefright: limit audio gap for looped playback

The audio gap when looping audio is mostly due to
a delay requested by the audio player when executing
the end of stream message. This is to allow the audio
to be drained out of the pipe before actually stopping the
AudioTrack.
This delay is not needed when looping as the AudioTrack
is not stopped.

The fix consists in ignoring the requested delay when the
looping flag is set in awesome player.

Issue 5800981.

Change-Id: Ib32d2930c53ecebc21ca8440e6e054c7e20db4a5