camera: Move the focus state set

Doing this on preview isn't enough. Solve the race condition by
cancelling ongoing focus messages if a new one is requested

Change-Id: I0c2268d44f18056fea0263c0a420c67eac106db6
Add mpdecision service

Change-Id: I69d22cdb0b6235f57476a072d6879c900f31dd3e