Transport work broke serving over http

When converting Loggerhead to use transports, the code to serve branches over http was changed to this:

        elif '/.bzr/' in environ['PATH_INFO']:
            app = urlparser.make_static(None, self.transport)
            return app(environ, start_response)

Passing a transport to make_static() leads to a long and complicated traceback, since it was expecting a string path.

(Thanks to aeropi in #bzr for noticing this.)