Properly init bta::av::bta_av_aact message structures 13/20 am: 52b501db am: 79228d70

Original change: https://android-review.googlesource.com/c/platform/packages/modules/Bluetooth/+/2323930



Change-Id: I451f7039e5263065c58c1a2ccb8d15de88b61611
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>