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

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

Change-Id: I62867724908a2663fc07599023c10a2f72a484ac