Remote volume changes

When the user plays media remotely, and presses on the volume
 keys with the screen off, verify whether not only local playback
 is active, but also if remote playback is active to see if
 the volume should be adjusted.
When adjusting the volume with screen off, adjust the remote
 volume if applicable.

When controlling volume, give priority to local media playback.

Bug 11169862

Change-Id: I88a8c003969177d50d4c1569ec6cd2a7c153a341