Properly init bta::av::bta_av_aact message structures 20/20 am: 165b2ca7

Original change: https://android-review.googlesource.com/c/platform/packages/modules/Bluetooth/+/2326217



Change-Id: I69f7270e50e413c261632cbeec50721984040480
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>