leaudio: Fix cleaning BtaGattQueue

If remote disconnects us, we should make sure, BtaGattQueue is empty.

Bug: 249431973
Test: atest BluetoothInstrumentationTests
Test: manual - puttin earbud in and out from the box
Tag: #feature
Merged-In: I0920ff4ade01298fd3e16c62d70e5018c060c538
Change-Id: I0920ff4ade01298fd3e16c62d70e5018c060c538
(cherry picked from commit 5d6159e1)