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 am: 25252c10

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



Change-Id: I2d9f068797cb89cd31bebb11d337c492f1559f33
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>