CNR: prevent duplicate nameservers in registrar corrections to fix #3985#3987

tlimoncelli merged 1 commit intoStackExchange:mainStackExchange/dnscontrol:mainfrom

centralnicgroup-opensource:RSRMID-2688-dns-control-useless-nameserver-updatecentralnicgroup-opensource/rtldev-middleware-dnscontrol:RSRMID-2688-dns-control-useless-nameserver-updateCopy head branch name to clipboard