Bluetooth: audio: Fix server ASE Release in Codec Configured state

This fixes issue where the ASE state stuck in Releasing state instead of
going to Idle/Codec Configured as test requires.
Looks like there was a race condition possible where the ASE
notification work was run before the stream was detached, so there was
no transition to idle state triggered.

Fixes: ASCS/SR/ACP/BV-24-C
Signed-off-by: Mariusz Skamra <mariusz.skamra@codecoup.pl>