leaudio: Improve connecting other set members

If user connects group, Java will start connecting all the devices in
the group. However if some devices are not in range, timer will fire and
connect will be canceled.
With this patch, in such a case, we will put device into white list and
start background connect, so device will get connected when ready

Bug: 150670922
Tag: #feature
Sponsor: jpawlowski@
Test: atest --host bluetooth_le_audio_test bluetooth_le_audio_client_test

Change-Id: I3f36c78502b5ac858ec158bc2a43d1baac9e008a