[bug report] after the El submenu is encapsulated into the component, the mouseenter event will be called recursively. The maximum call stack size exceeded

### Element UI version
2.13.2

### OS/Browsers version
win10/Chrome

### Vue version
2.6.11

### Reproduction Link
https://codepen.io/xiaoxin9039/pen/BajogOG

### Steps to reproduce
将el-submenu封装到组件的行为，都会在mouseenter事件中引起循环调用

### What is Expected?
没有循环调用，没有Maximum call stack size exceeded错误

### What is actually happening?
mouseenter事件中发生Maximum call stack size exceeded