AwesomePlayer: do not send events when paused.

When streaming audio and paused, AwesomePlayer should
stop sending BufferingEvents as they will keep a wake lock
for no reason.

TimedEventQueue should always acquire the wakelock with mediaserver
identity so that it is released with the same identity by the
event handler thread.

Bug: 11104408.
Change-Id: Ied0e03acd6ad2f5a4c0ec82d5c2aa4e1c6da772c