Ensure its natural to customize DefaultFlowUrlHandler to work when urlwrite turned on for clean urls

A best practice for webapps that use JSP views is to use UrlRewrite to map /* to /[dispatcher-servlet]/* servlet-mapping for clean urls that don't show the app front-controller servlet mapping path. DefaultFlowUrlHandler does not work with a UrlRewrite rule like this out of the box. We should investigate ways to allow it to easily work when UrlRewrite is in the picture.