Switch language name 'zh' to 'zh-cn'

This is the first step to rename 'zh' to 'zh-cn'. There are several reasons why we rename the language name.

- The upstream docsy theme changed the language name, leading to many warnings during site build;
  The side-effect is that the i18n strings are no longer working.
- We believe renaming the language is the right thing to do, because this move can make room for other variants of Chinese language, such as 'zh-tw', 'zh-sg' etc.

There would be several follow-ups to this PR, such as fixing the intra-site links, adding redirects etc.

We will lock up changes to zh/zh-cn pages for the moment, until this one gets in.

This PR is based on commit cdad0a7342.

content/zh-cn/docs/reference/setup-tools/kubeadm/generated/kubeadm_config.md

@@ -0,0 +1,113 @@
+<!--
+The file is auto-generated from the Go source code of the component using a generic
+[generator](https://github.com/kubernetes-sigs/reference-docs/). To learn how
+to generate the reference documentation, please read
+[Contributing to the reference documentation](/docs/contribute/generate-ref-docs/).
+To update the reference conent, please follow the 
+[Contributing upstream](/docs/contribute/generate-ref-docs/contribute-upstream/)
+guide. You can file document formatting bugs against the
+[reference-docs](https://github.com/kubernetes-sigs/reference-docs/) project.
+-->
+
+<!-- 
+Manage configuration for a kubeadm cluster persisted in a ConfigMap in the cluster 
+-->
+管理持久化在 ConfigMap 中的 kubeadm 集群的配置
+
+<!--
+### Synopsis
+-->
+
+### 概要
+
+<!--
+There is a ConfigMap in the kube-system namespace called "kubeadm-config" that kubeadm
+uses to store internal configuration about the cluster. kubeadm CLI v1.8.0+ automatically
+creates this ConfigMap with the config used with 'kubeadm init', but if you
+initialized your cluster using kubeadm v1.7.x or lower, you must use the 'config upload'
+command to create this ConfigMap. This is required so that 'kubeadm upgrade' can configure
+your upgraded cluster correctly.
+-->
+
+kube-system 命名空间里有一个名为 "kubeadm-config" 的 ConfigMap，kubeadm 用它来存储有关集群的内部配置。
+kubeadm CLI v1.8.0+ 通过一个配置自动创建该 ConfigMap，这个配置是和 'kubeadm init' 共用的。
+但是您如果使用 kubeadm v1.7.x 或更低的版本初始化集群，那么必须使用 'config upload' 命令创建该 ConfigMap。
+这是必要的操作，目的是使 'kubeadm upgrade' 能够正确地配置升级后的集群。
+
+```
+kubeadm config [flags]
+```
+
+<!--
+### Options
+-->
+
+### 选项
+
+   <table style="width: 100%; table-layout: fixed;">
+<colgroup>
+<col span="1" style="width: 10px;" />
+<col span="1" />
+</colgroup>
+<tbody>
+
+<tr>
+<td colspan="2">-h, --help</td>
+</tr>
+<tr>
+<td></td><td style="line-height: 130%; word-wrap: break-word;">
+<!-- 
+<p>help for config</p>
+-->
+<p>config 操作的帮助命令</p>
+</td>
+</tr>
+
+<tr>
+<td colspan="2">
+<!--
+--kubeconfig string&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Default: "/etc/kubernetes/admin.conf"
+-->
+--kubeconfig string&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;默认值："/etc/kubernetes/admin.conf"
+</td>
+</tr>
+<tr>
+<td></td><td style="line-height: 130%; word-wrap: break-word;">
+<!-- 
+<p>The kubeconfig file to use when talking to the cluster.
+If the flag is not set, a set of standard locations can be searched for an existing kubeconfig file.</p>
+-->
+<p>用于和集群通信的 kubeconfig 文件。如果它没有被设置，那么 kubeadm 将会搜索一个已经存在于标准路径的 kubeconfig 文件
+</td>
+</tr>
+
+</tbody>
+</table>
+
+<!--
+### Options inherited from parent commands
+-->
+
+### 从父命令继承的选项
+
+   <table style="width: 100%; table-layout: fixed;">
+<colgroup>
+<col span="1" style="width: 10px;" />
+<col span="1" />
+</colgroup>
+<tbody>
+
+<tr>
+<td colspan="2">--rootfs string</td>
+</tr>
+<tr>
+<td></td><td style="line-height: 130%; word-wrap: break-word;">
+<!-- 
+<p>[EXPERIMENTAL] The path to the 'real' host root filesystem.</p>  
+-->
+<p>[实验] 到 '真实' 主机根文件系统的路径。
+</td>
+</tr>
+
+</tbody>
+</table>