DO NOT MERGE : Ensure that the first post-restore backup pass is correct

Some restore passes bring an ancestral dataset to the application, but
others instead act to bring an app back into sync with its own most-
recently-saved data.  In the latter case the state file written by the
app after the restore is a correct basis for generating future backup
deltas, but in the former case it is not.

The app should not be required to distinguish between these cases;
the framework has all the information necessary to handle the saved
state correctly following any flavor of restore operation.  This
patch makes the Backup Manager properly cause a full backup pass
following an ancestral-dataset restore.  After a current-set
restore the saved state file is an accurate description for
purposes of continued backup operations, so is preserved.

(Cherrypick from master to gingerbread)

Change-Id: I4bc4e8782a168ecc0795107a340bdbb35060730e