1172 refactor authorization tests

Clean up and refactor authorization tests. More at http://dev.mconf.org/redmine/issues/1172
Ok, I agree with setting it to true. We already [validate the locales in the controller that sets them](https://github.com/mconf/mconf-web/blob/master/app/controllers/session_locales_controller.rb#L23), so setting an invalid locale would be a bug in the application -- better get an exception.