Handle SLC in MultiHFPending state

Use case:
Connect 2 headsets one after another in quick
succession.

Failure:
SLC for first headset is not happening.

Root cause:
SLC for first headset is not handled when second
headset is connecting.

Fix:
Add handling for SLC event for HS1 in MultiHFPending state.

Change-Id: If0c2553c28e233bea4622fca10c94fddd913afa7