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/cloud-provider.md

@@ -0,0 +1,65 @@
+---
+title: 云供应商（Cloud Provider）
+id: cloud-provider
+date: 2018-04-12
+short_description: >
+  一个提供云计算平台的组织。
+
+aka:
+- 云服务供应商（Cloud Service Provider）
+tags:
+- community
+---
+
+<!--
+---
+title: Cloud Provider
+id: cloud-provider
+date: 2018-04-12
+short_description: >
+  An organization that offers a cloud computing platform.
+
+aka:
+- Cloud Service Provider
+tags:
+- community
+---
+-->
+
+<!--
+ A business or other organization that offers a cloud computing platform.
+-->
+ 一个提供云计算平台的商业机构或其他组织。
+
+
+
+<!--more-->
+
+<!--
+Cloud providers, sometimes called Cloud Service Providers (CSPs), offer
+cloud computing platforms or services.
+
+Many cloud providers offer managed infrastructure (also called
+Infrastructure as a Service or IaaS).
+With managed infrastructure the cloud provider is responsible for
+servers, storage, and networking while you manage layers on top of that
+such as running a Kubernetes cluster.
+
+You can also find Kubernetes as a managed service; sometimes called
+Platform as a Service, or PaaS. With managed Kubernetes, your
+cloud provider is responsible for the Kubernetes control plane as well
+as the {{< glossary_tooltip term_id="node" text="nodes" >}} and the
+infrastructure they rely on: networking, storage, and possibly other
+elements such as load balancers.
+-->
+云供应商，有时也称作云服务供应商（CSPs）提供云计算平台或服务。
+
+很多云供应商提供托管的基础设施（也称作基础设施即服务或 IaaS）。
+针对托管的基础设施，云供应商负责服务器、存储和网络，而用户（你）
+负责管理其上运行的各层软件，例如运行一个 Kubernetes 集群。
+
+你也会看到 Kubernetes 被作为托管服务提供；有时也称作平台即服务或 PaaS。
+针对托管的 Kubernetes，你的云供应商负责 Kubernetes 的控制面以及
+ {{< glossary_tooltip term_id="node" text="节点" >}} 及他们所依赖的基础设施：
+网络、存储以及其他一些诸如负载均衡器之类的元素。
+