Avoid sending SCO disconnect when power mode is processing

Use case:
1. Pair and connect with Mercedes car kit.
2. Answer incoming call by phone or car kit.
3. Switch audio between car kit and phone.
4. Repease 1-3 steps.

Failure:
Car kit is going into bad state and not accepting SCO disconnect.

Root cause:
Phone has sent SCO disconnect command to car kit when
power mode command(sniff/unsniff) is in the processing
on the ACL where SCO is active. Car kit didn't accept
remove SCO request command and gone into bad state.

Fix:
AG should send sco disconnect once power mode change is completed
to avoid this failure.

Change-Id: I7eba162a8fd9615795009ab26005535a3e5c7e86