fix deadlock in MediaPlayerService

void MediaPlayerService::AudioOutput::close()

{

    ALOGV("close");

    sp<AudioTrack> track;

    {

        Mutex::Autolock lock(mLock);

    close_l();

        track = mTrack;

        close_l(); // clears mTrack

    }

    // destruction of the track occurs outside of mutex.

}

void MediaPlayerService::AudioOutput::setVolume(float left, float right)