When doing the HAL cleanup the callbacks should be reset to NULL
after calling hal_ipc_unregister otherwise an handler may be called
leading to invalid reads:
BlueZ D: android/hal-a2dp.c:cleanup()
bluetoothd[2624]: android/avdtp.c:connection_lost() Disconnected: Input/output error (5)
bluetoothd[2624]: android/avdtp.c:avdtp_ref() 0x5841900: ref=2
bluetoothd[2624]: android/a2dp.c:bt_a2dp_notify_state() device 00:AA:01:01:00:00 state 0
==2564== Thread 3:
==2564== Invalid read of size 8
==2564== at 0x6B66B47: handle_conn_state (hal-a2dp.c:38)
==2564== by 0x6B6CDB3: notification_handler (hal-ipc.c:125)
==2564== by 0x5368EE4: start_thread (in /usr/lib64/libpthread-2.18.so)
==2564== by 0x5672B8C: clone (in /usr/lib64/libc-2.18.so)
==2564== Address 0x8 is not stack'd, malloc'd or (recently) free'd
This header contains IPC specific structures and code not related to
BT and audio HAL protocols. This allows to fully decouple IPC from
HAL messages.
This is first step to make HAL part of IPC unit-testable and reusable
between BT HAL and audio HAL.
