prevent crash of CA-less server upgrade due to absent certmonger
    
    ipa-server-upgrade tests whether certmonger service is running before
    attempting to upgrade IPA master. This causes the upgrader to always fail when
    there is no CA installer and certmonger is not needed, effectively preventing
    CA-less IPA master to upgrade succefuly.
    
    This test is now skipped if CA is not enabled.
    
    https://fedorahosted.org/freeipa/ticket/5519
    
    Reviewed-By: Jan Cholasta <jcholast@redhat.com>