Merge "AS: only dispatch preferred mixer attributes change if the device is...

Merge "AS: only dispatch preferred mixer attributes change if the device is found." into udc-dev am: ceabef76

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/22126832



Change-Id: I40a47bed633404dc8ec9cf3e02a378b15bb8386a
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>