Avoid strict mode warning when persisting sync state

We need to be sure that the write of the SyncManager state is complete
when broadcast of ACTION_SHUTDOWN is complete, so doing it
asynchronously is not an alternative.

This will remove the strict mode warning.

Change-Id: I01897bcc4bc0226cc3b49d4a6361d0572614c74c

Conflicts:
	services/java/com/android/server/content/SyncManager.java