audio: Change mDeathHandler from a member into a local variable am: 17b32012 am: 58f954fd am: 927728cd

Original change: https://android-review.googlesource.com/c/platform/hardware/interfaces/+/2819040



Change-Id: Ia7ae3c2d5661a9132650996545725c55a26704a8
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>