pkinit enable: use local dogtag only if host has CA
    
    ipa-pkinit-manage enable is failing if called on a master
    that does not have a CA instance, because it is trying to
    contact dogtag on the localhost.
    The command should rather use certmonger in this case, and
    let certmonger contact the right master to request the KDC
    certificate.
    
    Fixes: https://pagure.io/freeipa/issue/7795
    Reviewed-By: Francois Cami <fcami@redhat.com>