leaudio: Fix device being not in allow list when group connected

This patch makes sure that when 1 group member connects, the others will
be added to allow list.

Also when all devices got disconnected, all of them will go back to
default reconnection mode.

Bug: 294615104
Test: atest bluetooth_le_audio_client_test
Tag: #feature
Change-Id: I3d9dfac11d85559172e3e054e5255c66e35c71e9