leaudio: Add set member to allow list if one set member is connected

With this patch, Android will always keep set member in the allow list,
if the other member is connected

Bug: 279990836
Test: atest BluetoothInstrumentationTests
Test: atest bluetooth_le_audio_client_test
Tag: #feature

Change-Id: I006239fe4dcffcd45b4823db841d8059676e8b27