Merge "AudioService: Register MASTER_BALANCE/MONO observer for all users" into main am: d40478ca7e am: bff7388f81

Original change: https://android-review.googlesource.com/c/platform/frameworks/base/+/2820598

Change-Id: Ie18dbaba23404381dd5a0b0e22411257b6f852a7
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>