to DNSSEC but are sematically equal according to plain
DNS. Apply plain DNS comparisons rather than DNSSEC
comparisons when processing UPDATE requests.
dnssec-signzone now removes such semantically duplicate
records prior to signing the RRset.
named-checkzone -r {ignore|warn|fail} (default warn)
named-compilezone -r {ignore|warn|fail} (default warn)
named.conf: check-dup-records {ignore|warn|fail};