Merge "[Ongoing Call] Always unregister the UidObserver." into sc-dev am: 3d1c180320 am: 35c1997024 am: 9de7969adf am: 12b2f1aa48

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/15503430

Change-Id: Id1709d12e415c0e3640b5295cf2f3d166b151f75