[Bug Report] Popover hide while trigger is `click`(not mouseup)

### Element UI version
2.13.2

### OS/Browsers version
win10x86 chrome 80

### Vue version
2.6.2

### Reproduction Link
http://www.serfend.top/#/application/newApply?via=github.com

### Steps to reproduce
1. select `username` `input` in `login form` (at the right top of the browser)
2. input arbitrarily letters
3. move mouse from right to left to select the `username``input` till out of the `Popover`
4. release the mouse

### What is Expected?
`click`-`trigger` should not effect on `Popover`

### What is actually happening?
`click`-`trigger` should effect on `Popover`