proxies / reverseproxy / candidate-registery: redirect top level to catalog
    
    See: https://pagure.io/fedora-infrastructure/issue/8507
    Currently https://candidate-registry.fedoraproject.org/ just gives you a
    blank page. So instead lets redirect to the catalog to at least show
    something to people.
    
    Signed-off-by: Kevin Fenzi <kevin@scrye.com>