NuPlayer: Fix ANR while resetting RTSP playback

- When network is poor, the response of RTSP teardown won't be received
  in time, so ANR will happen.
- With this patch, a teardown message will be sent when timeout expires,
  in order to avoid ANR.

Change-Id: I3f9efd9fefa66104ad452559ced5ff5218d73a66
CRs-Fixed: 650866
audio:Avoid VideoLagUpdate if there is no AudioPlayer

-When AudioTrack is failed to initialized, mAudioPlayer
 is deleted in onVideoEvent but onVideoLagUpdate() is still
 trying to access mAudioPlayer which is leading to a crash.
 The function onVideoLagUpdate() is used to notify if video
 is lagging behind audio. So this function is no longer
 valid if AudioPlayer is deleted.

-Fix is to add a check for AudioPlayer in onVideoLagUpdate,
 which will avoid onVideoLagUpdate() if there is no
 AudioPlayer

Change-Id: Ie8dbfc1995a3da88a4a435ec2de86b1c22a07c65
CRs-Fixed: 647200