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/glossary/cluster-operator.md

@@ -0,0 +1,45 @@
+---
+title: 集群操作者（Cluster Operator）
+id: cluster-operator
+date: 2018-04-12
+full_link: 
+short_description: >
+  配置、控制、监控集群的人。
+
+aka: 
+tags:
+- user-type
+---
+
+<!--
+---
+title: Cluster Operator
+id: cluster-operator
+date: 2018-04-12
+full_link: 
+short_description: >
+  A person who configures, controls, and monitors clusters.
+
+aka: 
+tags:
+- user-type
+---
+-->
+
+<!--
+ A person who configures, controls, and monitors clusters.
+-->
+ 配置、控制、监控集群的人。
+
+<!--more--> 
+<!--
+Their primary responsibility is keeping a cluster up and running, which may involve periodic maintenance activities or upgrades.<br>
+
+			
+**NOTE:** Cluster operators are different from the [Operator pattern](https://www.openshift.com/learn/topics/operators) that extends the Kubernetes API.
+-->
+
+他们的主要责任是保持集群正常运行，可能需要进行周期性的维护和升级活动。<br>
+
+**注意：** 集群操作者不同于[操作者模式（Operator Pattern）](https://www.openshift.com/learn/topics/operators)，操作者模式是用来扩展 Kubernetes API 的。
+