leaudio: Store LeAudio service handles when device is verified.

If device got disconnected while LeAudio service is connected, it could
stay in the state, that handles are known and stored, but LeAudio group
id is not yet know.
In such case, device will stay in wrong state.

This patch fixes it.
Bug: 296761332
Test: atest bluetooth_le_audio_client_test
Tag: #feature

Change-Id: I8f58fa65c8cd7a7f334605f73c8dd75666877e58