QuietHours: disable volume change tone during quiet hours

* Its quiet time, you're trying to be quiet, why would the volume
  change make noise when you're being quiet?
* Turn this off when system sounds are disabled during quiet hours

Change-Id: I6c7eb9d52f5dab9349bf2b8f72ddcb0ab45834fa
Merge "QuietHours: disable volume change tone during quiet hours" into cm-11.0