Revert "remove headset volume warning"

This reverts commit 6e4f854ebcd37f130bdeb5ef6f572465777e65f1.
Framework: safe headset volume option (1 of 2)

thanks DvTonder

Change-Id: I5355820a24d48c1d8f54ea17a7022d891ad07857
(cherry picked from commit 4185583e01daf81207c71f1002dfa1a6e998ad74)

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