dcb6916 fix force-sync, re-initialize of replica and a check for replication agreement existence

Authored and Committed by pvoborni 8 years ago
    fix force-sync, re-initialize of replica and a check for replication agreement existence
    
    in other words limit usage of `agreement_dn` method only for manipulation
    and search of agreements which are not managed by topology plugin.
    
    For other cases is safer to search for the agreement.
    
    https://fedorahosted.org/freeipa/ticket/5066
    
    Reviewed-By: David Kupka <dkupka@redhat.com>