Properly init bta::av::bta_av_aact message structures 20/20 am: 165b2ca7 am: be4365e9

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



Change-Id: I22224d42dc6691f2fd2e02b7114b27a802a004ad
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>