Bluetooth: Added PHONE_ON_DISCONNECT event.

This will help in getting the call
disconnect event properly as sometimes
in three way call states, the
PRECISE_CALL_STATE_CHANGED is missed
and application fails to update call
disconnect state to BT app.

CRs-Fixed: 552239
Change-Id: I55f5bea9e2437149db5946bc01acb66ae99038b0
Bluetooth: Update the call held status.

This change makes sure to update the
single held call state when an active call
is dropped in three way call scenario.

CRs-Fixed: 555450
Change-Id: I9ed4c9d018c6e5da9735137990df979a74bab03f
Merge "Bluetooth: Update the call held status."
Merge "Bluetooth: Added PHONE_ON_DISCONNECT event."
Merge remote-tracking branch 'caf/jb_mr2' into caf