bugfix: fix last modify by not update bug

apollo-portal/src/main/java/com/ctrip/framework/apollo/portal/controller/ItemController.java

@@ -68,6 +68,9 @@ public class ItemController {
                          @RequestBody ItemDTO item) {
     checkModel(isValidItem(item));
 
+    String username = userInfoHolder.getUser().getUserId();
+    item.setDataChangeLastModifiedBy(username);
+
     configService.updateItem(appId, Env.valueOf(env), clusterName, namespaceName, item);
   }
 

apollo-portal/src/main/java/com/ctrip/framework/apollo/portal/service/ItemService.java

@@ -99,10 +99,6 @@ public class ItemService {
   }
 
   public void updateItem(String appId, Env env, String clusterName, String namespaceName, ItemDTO item) {
-    if (StringUtils.isEmpty(item.getDataChangeLastModifiedBy())) {
-      String username = userInfoHolder.getUser().getUserId();
-      item.setDataChangeLastModifiedBy(username);
-    }
     itemAPI.updateItem(appId, env, clusterName, namespaceName, item.getId(), item);
   }