leaudio: Clear configuration cache when device got disconnected.

Make sure when device will try to attach to the stream after
disconnection, it will generate new configution valid for the connected
devices in the group

Bug: 304538560
Test: atest bluetooth_le_audio_test
Tag: #feature
Change-Id: Ifa6871f2ec384b59cd20e4d20c3945fb23ad3754