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/job.md

@@ -0,0 +1,46 @@
+---
+title: Job
+id: job
+date: 2018-04-12
+full_link: /zh/docs/concepts/workloads/controllers/job/
+short_description: >
+  Job 是需要运行完成的确定性的或批量的任务。
+
+aka: 
+tags:
+- fundamental
+- core-object
+- workload
+---
+
+<!--
+---
+title: Job
+id: job
+date: 2018-04-12
+full_link: /docs/concepts/workloads/controllers/job/
+short_description: >
+  A finite or batch task that runs to completion.
+
+aka: 
+tags:
+- fundamental
+- core-object
+- workload
+---
+-->
+
+<!--
+ A finite or batch task that runs to completion.
+-->
+
+ Job 是需要运行完成的确定性的或批量的任务。
+
+<!--more--> 
+
+<!--
+Creates one or more {{< glossary_tooltip term_id="pod" >}} objects and ensures that a specified number of them successfully terminate. As Pods successfully complete, the Job tracks the successful completions.
+-->
+
+Job 创建一个或多个 {{< glossary_tooltip term_id="Pod" >}} 对象，并确保指定数量的 Pod 成功终止。
+随着各 Pod 成功结束，Job 会跟踪记录成功完成的个数。