Remove debug console.log and optimize object copy

Fixes #2380

lib/cluster.js

@@ -29,11 +29,10 @@ function isObject(o) {
 }
 
 function extendObject(origin, add) {
-  console.log('object: ', add);
-  for (var name in add) {
-    if (Object.hasOwnProperty.call(add, name)) {
-      origin[name] = add[name];
-    }
+  var keys = Object.keys(add),
+      i = keys.length;
+  while(i--) {
+    origin[keys[i]] = add[keys[i]];
   }
   return origin;
 }