#436 list only lists from the requested domain

[The Anarcat]

In Mailman 2.1, the listinfo page lists all pages
belonging to the current vhost. Or not exactly. It
lists all lists that have the current vhost in their
web_page_url. Which is wrong, because if I have a list
like list@sub.example.com and visit
http://example.com/mailman/listinfo, it *will* be
listed. I would expect it to be listed only if I visit
http://sub.example.com/mailman/listinfo.

This one-line patch fixes this.

[The Anarcat]