Make UserManager enforce user restrictions, not DPM.

- Now even if a user restriction is set via UserManager, it'll be correctly
enforced.

- Changed the way AudioService enforces the OP_MUTE_MICROPHONE and
OP_AUDIO_MASTER_VOLUME app ops -- previously, when they're set, even a muting
call would be rejected.  This was why DPMS.setUserRestriction() used different
calling orders for DISALLOW_UNMUTE_MICROPHONE/DISALLOW_ADJUST_VOLUME depending
on setting them or clearing them.
Now, even when the app ops are set, we still allow muting calls.

Bug 23902097
Bug 24981972

Change-Id: I865b5de43e15f5955f94006475a5ec6254904d31