base

Fix deadlock in BackupManagerService

Lock ordering bug.  The fix is to avoid having to hold both locks
simultaneously in one prong of the deadlock.  (Further strengthening:
the code path for potentially acquiring both simultaneously now
begins at a common method, ensuring that lock ordering is always
consistent.)

Change-Id: If9433aff8326fec2ba0e97e96ad2d835b01e2cda