当状态为loading时，再次下拉或加载scrollTop为0了，但top-load-method还没结束

[tengfei5000nian]

handleTouchEnd(event) {
event.stopPropagation();
if (this.diff !== 0) {
if (this.state === 'trigger') {//这里应该还要考虑state='loading'
this.actionLoading();
return;
}

      // pull cancel
      this.scrollTo(0);
    }
  },