Prevent lock/unlock sound during music playback

Lock/unlock sound mixes in with music and causes
lag and distortion.

Change-Id: I9d3582c6bf28aa62a5a6712bc9e89eb2f73e0288
MediaFocusControl: Do not grant audio focus if notification stream is 0

Previously audio focus would be granted regardless of notification volume, meaning
that if notifications are muted the media stream would still be dimished for focus.
By checking if STREAM_NOTIFICATION is 0 and if a notification stream is
requesting focus, this no longer an issue.

PS1: Initial implement
PS2: Better implement in MediaFocusControl
PS3: Whitespace

Change-Id: Ie10a64e58ce77174a3bbdeaa936646d40c24404f
Signed-off-by: Evan Anderson <evan1124@gmail.com>
Merge changes Ie10a64e5,I9d3582c6 into kitkat

* changes:
  MediaFocusControl: Do not grant audio focus if notification stream is 0
  Prevent lock/unlock sound during music playback