Add audiotrack unit tests am: ba55d5a5 am: 6b2a85a7

Original change: https://android-review.googlesource.com/c/platform/frameworks/av/+/2189999



Change-Id: I4a93570f3064f7fbf443a054b52f455a9da91f29
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>