install: merge all CA install code paths into one
    
    Merge CA install code paths use in ipa-server-install, ipa-replica-install
    in either domain level and ipa-ca-install into one.
    
    https://fedorahosted.org/freeipa/ticket/6392
    
    Reviewed-By: Stanislav Laznicka <slaznick@redhat.com>