Fix DL1 replica installation in CA-less topology
    
    Commit dbb98765d73519289ee22f3de1a5ccde140f6f5d changed certmonger
    requests for DS and HTTP certificates during installation to raise
    on error (https://fedorahosted.org/freeipa/ticket/6514).
    This introduced a regression in DL1 replica installation in CA-less
    topology.  A certificate was requested, but prior to the
    aforementioned commit this would fail silently and installation
    continued, whereas now installation fails.
    
    Guard the certificate request with a check that the topology is
    CA-ful.
    
    Fixes: https://fedorahosted.org/freeipa/ticket/6573
    Reviewed-By: Martin Babinsky <mbabinsk@redhat.com>