feat: update keystone-rxt to use the new rxt role (#6) This change makes it possible to run the keystone rxt plugin in an environment using the os_flex attribute. This change includes * multi-account detection and autoprovisioning * new mapping defaults for scheme version 2.0 Two new options have been added to support the creation of the role attribute methods, allowing a user to be a member of more than one project. [rackspace] role_attribute_enforcement <BOOL> role_attribute <STR> Signed-off-by: Kevin Carter <kevin.carter@rackspace.com>