Fix Issue 2158631: AudioService: volume control sometimes not restored after...

Fix Issue 2158631: AudioService: volume control sometimes not restored after media server process crash.

The problem comes from the fact that the AudioSystem callback indicating that the media server is active again is ignored if it is received before the delayed message indicating media server death. This happens if another application or service running in the system server process makes a request to the AudioSystem in the interval between the death of the media server and the reception of the corresponding delayed message.

The fix consists in resetting mMediaServerOk flags immediately when the death callback is received and not when the delayed message is received.