revert removal of cn attribute from idnsRecord
The removal, which was done in IPA-3.2, causes replication issues between IPA < 3.2 and IPA 4.1. Because IPA 4.1 adds two more attributes.
https://fedorahosted.org/freeipa/ticket/4794
Reviewed-By: Thierry Bordaz <tbordaz@redhat.com>
Reviewed-By: Jan Cholasta <jcholast@redhat.com>