As far as I know this is not officially supported and there is no proper way to do that what you want. There are some guides on the internet on how to change this URL behavior in the endpoints.conf configuration file of the rhttpproxy. However, none of this works for rewriting the complete URL. And I wouldn't recommend you experimenting with it on a productive system either.
But what exactly do you want to achieve? What bothers you about this URL and why do you want to change it at all?