audio: Change mDeathHandler from a member into a local variable am: 17b3201259

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

Change-Id: I606293ee74df3175ebc3b2cea21cc1e8c1be511f
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>