dns checker returns empty string for fqdn resolting in wrong error message
I had an issue with a machine that the FQDN was not resolved by Ruby (but other programs did).
But instead of empty array, it returned an empty string inside an array as a single element.
The dns.rb checker then tried to resolve the ip address using 'reverse = Resolv.getname(ip.to_s)', but failed, entered the attempt to resolve it as IPv6, and return an error about resoling IPv6.
I think it is related to https://projects.theforeman.org/issues/23754 but not the same, but the issue is the actual ability to report the right message, and not to try and tell that there is no resolving for IPv6, that does not exists in the first place.