Convert ipa-pki-proxy.conf to use mod_ssl directives
    
    Related: https://pagure.io/freeipa/issue/3757
    Reviewed-By: Christian Heimes <cheimes@redhat.com>
    Reviewed-By: Stanislav Laznicka <slaznick@redhat.com>
    Reviewed-By: Rob Crittenden <rcritten@redhat.com>