AddChild test fix

`sortAllChildren` should not be part of the test.
It is tested separatedly on another test

samples/Cpp/TestCpp/Classes/PerformanceTest/PerformanceNodeChildrenTest.cpp

@@ -543,11 +543,11 @@ void AddSpriteSheet::update(float dt)
         {
             batchNode->addChild( sprites[i], zs[i], kTagBase+i);
         }
-        
-        batchNode->sortAllChildren();
-        
         CC_PROFILER_STOP(this->profilerName());
 
+
+        batchNode->sortAllChildren();
+
         // remove them
         for( int i=0;i <  totalToAdd;i++)
         {