Merge "Add new shutdown observer for MountService. Use new observer before...

Merge "Add new shutdown observer for MountService. Use new observer before rebooting and shutting down. Add some unit tests for unmount and shutdown code paths Fix registering/unregistering part in MountService Use ShutdownThread in PowerManager.reboot() Add reboot support to ShutdownThread. Remove MountService code from PowerManagerService.java and Power.java. Clean shutdown/reboot is handled exclusively by ShutdownThread now."