Audio streaming error when playing a stream that contains "end of file".

Although EOS is being posted upon receipt of BYE message from RTSP
server, still it didn't reach the media framework and application.
This happens because the Nuplayer::Renderer::onDrainAudioQueue() funtion
returns false after mAudioSink->getPosition() call , and the EOS message
present in mAudioQueue was lost.The mAudioSink->getPosition() returns
NO_INIT as mAudioSink->open() is not yet called,
hence no audio track exists in MediaPlayerService::AudioOutput.

Change-Id: I905e8f3af87dc778952eeef3904c4e2a6a75ca7a
Signed-off-by: Arulselvan M <arulselvan.m@intel.com>
Signed-off-by: Jin Wei <wei.a.jin@intel.com>