leaudio: Make sure to clean bta queue on BT OFF

Bug: 228351333
Test: atest BluetoothInstrumentationTests
Test: manual: BT OFF while LeAudio is streaming, BT ON start stream
Tag: #feature

Merged-In: I771efe95d30fdf97939d05e9e6d724cdb675b7f7
Change-Id: I771efe95d30fdf97939d05e9e6d724cdb675b7f7
(cherry picked from commit 68215ef0)