Clean up Safe headset volume code [1/2]

Credits: CM

Change-Id: I40e26f30f336e92e3efbac251c6091d1521297f5

Conflicts:
	core/java/android/provider/Settings.java
	media/java/android/media/AudioService.java
Option to use volume keys to control media volume anytime (2/2)

See Settings part for description

Change-Id: I78d26b0bd41f5b58514ae9c68208a8c950396823

Conflicts:
	media/java/android/media/AudioService.java