Update keystone config to clear warnings

These options were causing deprecation warnings. A couple of these are
now different from the stable/juno defaults, but that's because these
defaults were fixed after the stable branch was created. These changes
should not alter current behavior, other than clearning the deprecation
warnings.

xml_body middleware is deprecated, and removed in kilo
token driver path changed
token_format is now driver under [token]
revoke default driver path changed