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/kube-controller-manager.md

@@ -0,0 +1,47 @@
+---
+title: kube-controller-manager
+id: kube-controller-manager
+date: 2018-04-12
+full_link: /docs/reference/generated/kube-controller-manager/
+short_description: >
+  主节点上运行控制器的组件。
+
+aka: 
+tags:
+- architecture
+- fundamental
+---
+
+<!--
+---
+title: kube-controller-manager
+id: kube-controller-manager
+date: 2018-04-12
+full_link: /docs/reference/generated/kube-controller-manager/
+short_description: >
+  Component on the master that runs controllers.
+
+aka: 
+tags:
+- architecture
+- fundamental
+---
+-->
+
+<!--
+ Control plane component that runs 
+ {{< glossary_tooltip text="controller" term_id="controller" >}} processes.
+-->
+[kube-controller-manager](/zh/docs/reference/command-line-tools-reference/kube-controller-manager/) 是{{< glossary_tooltip text="控制平面" term_id="control-plane" >}}的组件，
+负责运行{{< glossary_tooltip text="控制器" term_id="controller" >}}进程。
+
+<!--more-->
+<!--
+Logically, each {{< glossary_tooltip text="controller" term_id="controller" >}} 
+is a separate process, but to reduce complexity, 
+they are all compiled into a single binary and run in a single process.
+--> 
+从逻辑上讲，
+每个{{< glossary_tooltip text="控制器" term_id="controller" >}}都是一个单独的进程，
+但是为了降低复杂性，它们都被编译到同一个可执行文件，并在同一个进程中运行。
+