Fixed the bug that application calls sum incorrect. Because of merge method...

Fixed the bug that application calls sum incorrect. Because of merge method return a non merged value .

apm-collector/apm-collector-stream/src/main/java/org/skywalking/apm/collector/stream/worker/impl/AggregationWorker.java

@@ -73,7 +73,7 @@ public abstract class AggregationWorker extends AbstractLocalAsyncWorker {
         Data data = (Data)message;
         dataCache.writing();
         if (dataCache.containsKey(data.id())) {
-            getRole().dataDefine().mergeData(data, dataCache.get(data.id()));
+            getRole().dataDefine().mergeData(dataCache.get(data.id()), data);
         } else {
             dataCache.put(data.id(), data);
         }