dogtaginstance: track server certificate with our renew agent
    
    Track Dogtag's server certificate with dogtag-ipa-ca-renew-agent instead of
    dogtag-ipa-renew-agent.
    
    https://fedorahosted.org/freeipa/ticket/5959
    
    Reviewed-By: Stanislav Laznicka <slaznick@redhat.com>
    Reviewed-By: Alexander Bokovoy <abokovoy@redhat.com>