leaudio: Always disconnect group on the transition timeout

With this patch if remote devices stop to response, the group will get
disconnected

Bug: 216466543
Bug: 150670922
Test: atest --host bluetooth_le_audio_test
bluetooth_le_audio_client_test
Sponsor: @jpawlowski

Change-Id: Iff2ea989a3a896bf8099eeba5c23e8487a176d42