zonemaster-engine

Methods 'Zonemaster::Engine::TestMethodsV2::get_{zone,del}_ns_names_and_ips()' can return a mix of Zonemaster::Engine::Nameserver or Zonemaster::Engine::DNSName objects, depending on whether the name could be resolved into an IP address.
Due to a previous oversight, this can cause issues in Test Cases that use them. We can filter Zonemaster::Engine::DNSName objects out since they can't be queried.