Revert "cups service: fix client sockets"

This reverts commit cf4c07734364e7e59414f486381360b42a9f88ea.

nixos/modules/services/printing/cupsd.nix

···
 
       listenAddresses = mkOption {
         type = types.listOf types.str;
-        default = [ "localhost:631" ];
+        default = [ "127.0.0.1:631" ];
         example = [ "*:631" ];
         description = ''
           A list of addresses and ports on which to listen.
···
             ''}
           '';
 
-          serviceConfig = {
-            PrivateTmp = true;
-            RuntimeDirectory = [ "cups" ];
-          };
+          serviceConfig.PrivateTmp = true;
       };
 
     systemd.services.cups-browsed = mkIf avahiEnabled

nixos/tests/printing.nix

···
       $client->waitForUnit("cups.service");
       $client->sleep(10); # wait until cups is fully initialized
       $client->succeed("lpstat -r") =~ /scheduler is running/ or die;
-      # Test that UNIX socket is used for connections.
-      $client->succeed("lpstat -H") =~ "/var/run/cups/cups.sock" or die;
-      # Test that HTTP server is available too.
+      $client->succeed("lpstat -H") =~ "localhost:631" or die;
       $client->succeed("curl --fail http://localhost:631/");
       $client->succeed("curl --fail http://server:631/");
       $server->fail("curl --fail --connect-timeout 2  http://client:631/");