Ensure the URL to koji points to the kojihub
    
    Otherwise, we may endpoint pointing at the web UI instead of the
    xmlrpc interface, which makes koji (the module) fail to run.
    It basically ends up throwing a bunch of ResponseError() as
    html and xmlrpc aren't quite the same thing.
    
    Signed-off-by: Pierre-Yves Chibon <pingou@pingoured.fr>