[bug report] the emitpath property of El cascade is set to false, and the value obtained is not the value of the last node

### Element UI version
2.14.1

### OS/Browsers version
win10

### Vue version
2.6.10

### Reproduction Link
https://codepen.io/eleven-wang/pen/LYRjyrp

### Steps to reproduce
将emit-path设置为"false"，change方法触发的时候打印出value的值

### What is Expected?
返回应该是该节点的值

### What is actually happening?
实际返回由该节点所在的各级菜单的值所组成的数组