can not destory dom when set property loop: true

[ManfredHu]

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BUG REPORT TEMPLATE

Vue.js version and component version

Reproduction Link

• A minimal JSBin, JSFiddle, Codepen, or a GitHub repository that can reproduce the bug.
• You could start with this template: https://jsfiddle.net/39epgLj0/

Steps to reproduce

What is Expected?

set property loop: true will create a div which classname is swiper-item swiper-slide swiper-slide-duplicate. But it can not to destory or delete when i switch to other page

In loop mode, duplicate slides are not being updated when the contents of the original slides change

What is actually happening?

[surmon-china]

Fixed with v4.x.

(: