[21.05] nixos/kresd: tell resolveconf to use local resolver

[dotlambda]

Motivation for this change

backport #124391

Things done

• Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS linux)
• Built on platform(s)
  • NixOS
  • macOS
  • other Linux distributions
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Added a release notes entry if the change is major or breaking
• Fits CONTRIBUTING.md.

[vcunat]

I wonder if this is small enough not to have a changelog mention. I'd probably leave it without any. (say, bind would be different because you can use it as authoritative-only server)

[ajs124]

this broke my setup. kthxbye.

for real though, not everyone has kresd listening on localhost.

[vcunat]

Yes, I was aware that it isn't 100%, but it's not just kresd and it's trivial to override.

In any case, I'm curious about possible motivation to run a resolver but not use it for the local system.

[ajs124]

It is used on the local system, just not through 127.0.0.1.