add_bind_root does not quote url

This was causing problem when calling `get_all_server_details` on #789 branch. That function appends limit and marker as query string and `add_bind_root` was quoting it resulting in `GET ../servers/detail%3Flimit%3D100` resulting in 404 from Nova for all requests. Since this function binds base to a full URL it is best if the caller does the quoting before passing the URL.
One problem with this is that it will break if we pass a unicode for either the root or the path. I guess we don't have any explicit tests for this in bind_root_url, but I *seem* to recall this being important.