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."