Don't change directories when opening non listable urls

For example, if you open http://foo.com/bar/myfile.pdf you don't want to do the trick of changing dir to http://foo.com/bar and opening myfile.pdf, because if we do that the next time you open the file dialog it will try to list http://foo.com/bar and won't work, which is kind of confusing, so just do that for listable protocols, where it makes sense that if i open a file from /home/albert/documents/kde/myfile.pdf the next time i open the file dialog it's at /home/albert/documents/kde