Release wakelocks acquired by SyncManager

Release the wakelocks internally acquired by SyncManager to improve
power performance.

Change-Id: I6d9663292cb4471d92ed9132beb7ed1ba2e8128f
CRs-Fixed: 585825
A background started service is removed from mStartingBackground when timeout.
Fix is to make sure mStartingBackground is updated to remove one.

Change-Id: I0e42beb550d33e6e400349b85bbb89848e18d520
Fix, MountService now only sends one onShutDownComplete

The event onShutDownComplete are sent only when all
volumes are shutdown. (Not one for every volume.)

Change-Id: I6af521ee8285ca581efac7d3c5f013dfbff3ee30