Change reference to kubeadm-stacked-color.png

Since the image is now moved to this repo, I'm changing all
references to the image to have them point to the local one.

content/zh/docs/setup/production-environment/tools/kubeadm/create-cluster-kubeadm.md

@@ -21,7 +21,7 @@ weight: 30
 `kubeadm` also supports other cluster
 lifecycle functions, such as [bootstrap tokens](/docs/reference/access-authn-authz/bootstrap-tokens/) and cluster upgrades.
 -->
-<img src="https://raw.githubusercontent.com/kubernetes/kubeadm/master/logos/stacked/color/kubeadm-stacked-color.png" align="right" width="150px">使用 `kubeadm`，你
+<img src="/images/kubeadm-stacked-color.png" align="right" width="150px">使用 `kubeadm`，你
 能创建一个符合最佳实践的最小化 Kubernetes 集群。事实上，你可以使用 `kubeadm` 配置一个通过 [Kubernetes 一致性测试](https://kubernetes.io/blog/2017/10/software-conformance-certification) 的集群。
 `kubeadm` 还支持其他集群生命周期功能，
 例如 [启动引导令牌](/zh/docs/reference/access-authn-authz/bootstrap-tokens/) 和集群升级。

content/zh/docs/setup/production-environment/tools/kubeadm/install-kubeadm.md

@@ -23,7 +23,7 @@ card:
 <img src="https://raw.githubusercontent.com/kubernetes/kubeadm/master/logos/stacked/color/kubeadm-stacked-color.png" align="right" width="150px">This page shows how to install the `kubeadm` toolbox.
 For information on how to create a cluster with kubeadm once you have performed this installation process, see the [Using kubeadm to Create a Cluster](/docs/setup/production-environment/tools/kubeadm/create-cluster-kubeadm/) page.
 -->
-<img src="https://raw.githubusercontent.com/kubernetes/kubeadm/master/logos/stacked/color/kubeadm-stacked-color.png" align="right" width="150px">本页面显示如何安装 `kubeadm` 工具箱。
+<img src="/images/kubeadm-stacked-color.png" align="right" width="150px">本页面显示如何安装 `kubeadm` 工具箱。
 有关在执行此安装过程后如何使用 kubeadm 创建集群的信息，请参见
 [使用 kubeadm 创建集群](/zh/docs/setup/production-environment/tools/kubeadm/create-cluster-kubeadm/) 页面。