hooks: Call the callback when done

If a hook function neither calls the callback nor returns a
(non-undefined) value then there's no way for the hook system to know
if/when the hook function has finished.

src/node/hooks/express/specialpages.js

@@ -87,5 +87,5 @@ exports.expressCreateServer = function (hook_name, args, cb) {
     });
   });
 
-
+  return cb();
 }