[Bug Report] DateTimePicker to form banned bug

[zhaixinhua]

Element UI version

2.4.6

OS/Browsers version

Win10/google，Mac/google

Vue version

2.5.17

Reproduction Link

https://jsfiddle.net/zhaixinhua/za6dsxg2/

Steps to reproduce

1.设置禁选日期；（例子中已设置）
2.更改上面的输入框中的时间为禁选的时间
3.确认保存
4.发现日期为禁选的日期

What is Expected?

禁选日期无论在哪里输入永远禁选

What is actually happening?

禁选日期仅仅不能点选，但能输入选择

[element-bot]

Translation of this issue:

Element UI version
2.4.6

OS/Browsers version
Win10/google, Mac/google

Vue version
2.5.17

Reproduction Link
https://jsfiddle.net/zhaixinhua/za6dsxg2/

Steps to reproduce

1. setting up the forbidden date; (set in the example)

2. change the time in the input box above is forbidden time.

3. confirm preservation

4. find date is prohibited.
   What is Expected?

No choice date, no matter where to enter, always banned.
What is actually happening?

No date can be selected, but it can be entered.

[ziyoung]

无法重现。

[zhaixinhua]

[ziyoung]

还是无法重现。是不是你电脑的时间修改过了？

[zhaixinhua]

你那个上面没有输入框，我是通过输入框更改的，不是选择的