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>