Update CentralAuth for Password API

Once I0a9c972931a0eff0cfb2619cef3ddffd03710285 is merged, this should
be added to CentralAuth to take advantage of the new api.

Note, CentralAuth functions just fine without this, but user's hashes
aren't upgraded to the site's new format on login without this change.

Bug: 68784
Change-Id: I9cb7bd09becb06c9e02b7425bdd10ae2cf8783af