Fix relative links issue in zh content (#13312)

* `http://kubernetes.io/docs/` -> `/docs/`

* `https://kubernetes.io/docs/` -> `/docs/`

content/zh/docs/reference/glossary/flexvolume.md

@@ -2,7 +2,7 @@
 title: Flexvolume
 id: flexvolume
 date: 2018-06-25
-full_link: https://kubernetes.io/docs/concepts/storage/volumes/#flexvolume
+full_link: /docs/concepts/storage/volumes/#flexvolume
 short_description: >
     Flexvolume 是创建 out-of-tree 卷插件的一种接口。 {{< glossary_tooltip text="容器存储接口（CSI）" term_id="csi" >}} 是比 Flexvolume 更新的接口，它解决了 Flexvolumes 的一些问题。
 
@@ -17,7 +17,7 @@ tags:
 title: Flexvolume
 id: flexvolume
 date: 2018-06-25
-full_link: https://kubernetes.io/docs/concepts/storage/volumes/#flexvolume
+full_link: /docs/concepts/storage/volumes/#flexvolume
 short_description: >
     Flexvolume is an interface for creating out-of-tree volume plugins. The {{< glossary_tooltip text="Container Storage Interface" term_id="csi" >}} is a newer interface which addresses several problems with Flexvolumes.
 
@@ -41,11 +41,11 @@ FlexVolume 驱动程序的二进制文件和依赖项必须安装在主机上。
 如果可能的话，SIG Storage 建议实现 {{< glossary_tooltip text="CSI" term_id="csi" >}} 驱动程序，因为它解决了 Flexvolumes 的限制。
 
 <!--
-* [Flexvolume in the Kubernetes documentation](https://kubernetes.io/docs/concepts/storage/volumes/#flexvolume)
+* [Flexvolume in the Kubernetes documentation](/docs/concepts/storage/volumes/#flexvolume)
 * [More information on Flexvolumes](https://github.com/kubernetes/community/blob/master/contributors/devel/flexvolume.md)
 * [Volume Plugin FAQ for Storage Vendors](https://github.com/kubernetes/community/blob/master/sig-storage/volume-plugin-faq.md)
 -->
 
-* [Kubernetes 文档中的 Flexvolume](https://kubernetes.io/docs/concepts/storage/volumes/#flexvolume)
+* [Kubernetes 文档中的 Flexvolume](/docs/concepts/storage/volumes/#flexvolume)
 * [更多关于 Flexvolumes 的信息](https://github.com/kubernetes/community/blob/master/contributors/devel/flexvolume.md)
 * [存储供应商的卷插件 FAQ](https://github.com/kubernetes/community/blob/master/sig-storage/volume-plugin-faq.md)