kippo: mark as broken

no successful hydra build since 2017-12-11

pkgs/servers/kippo/default.nix

···
       license = licenses.bsd3;
       platforms = platforms.linux;
       maintainers = with maintainers; [ tomberek ];
+      broken = true; # 2018-09-12, failed on hydra since 2017-12-11
     };
 }