音频播放器进度条拖拽mousedown事件和播放进度条点击事件冲突了

aplayer进度条在拖拽的时候，可能会出现无效情况，直接回到起点位置，经过测试，mousedown事件和播放进度条事件冲突了，所以取消进度条点击事件，因为mousedown的时候相当于做了一次点击事件

If you want to report a bug, please provide the following information:

- The steps to reproduce.
- A minimal demo of the problem via https://jsfiddle.net or http://codepen.io/pen if possible.
- Which versions of APlayer, and which browser / OS are affected by this issue?
1.10.1