haskell-happstack-server: disable 'doCheck' to avoid test suite build errors

tests/Test.hs:3:8:
    Could not find module `Happstack.Server.Tests'
    Perhaps you meant
      Happstack.Server.Types (from happstack-server-7.1.6)
      Happstack.Server.Auth (from happstack-server-7.1.6)
      Happstack.Server.Client (from happstack-server-7.1.6)
    Use -v to see a list of the files searched for.

pkgs/development/libraries/haskell/happstack/happstack-server.nix

@@ -16,6 +16,7 @@ cabal.mkDerivation (self: {
     utf8String xhtml zlib
   ];
   testDepends = [ HUnit parsec zlib ];
+  doCheck = false;
   meta = {
     homepage = "http://happstack.com";
     description = "Web related tools and services";