EE load balancing: NoMethodError: undefined method `size' for #<IPAddr: IPv4:127.0.0.1/255.255.255.255>

https://sentry.gitlab.net/gitlab/gitlabcom/issues/688524/

NoMethodError: undefined method `size' for #<IPAddr: IPv4:127.0.0.1/255.255.255.255>
  net/dns/resolver.rb:1006:in `query'
    @logger.info "Received #{ans[0].size} bytes from #{ans[1][2] + ':' + ans[1][1].to_s}"
  net/dns/resolver.rb:865:in `search'
    ans = query(name, type, cls)
  gitlab/database/load_balancing/service_discovery.rb:102:in `addresses_from_dns'
    resources = resolver.search(record, Net::DNS::A).answer
  gitlab/database/load_balancing/service_discovery.rb:67:in `refresh_if_necessary'
    interval, from_dns = addresses_from_dns
  gitlab/database/load_balancing/service_discovery.rb:40:in `block (2 levels) in start'
    refresh_if_necessary
...
(2 additional frame(s) were not displayed)

NoMethodError: undefined method `size' for #<IPAddr: IPv4:127.0.0.1/255.255.255.255>