Guard MediaDeviceManager.Entry against successive stop calls am: ae173fef18

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/20008426

Change-Id: Ie343026b0e079607b19cf55614e1c838ddbb7feb
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>