修复上传时的状态传递

onstart 时设置的是被封装后的对象的属性，这里直接传 file 的话没有 status/percent 属性.

components/upload/index.jsx

@@ -142,7 +142,7 @@ const AntUpload = React.createClass({
     targetItem.percent = e.percent;
     this.onChange({
       event: e,
-      file,
+      file: targetItem,
       fileList: this.state.fileList
     });
   },