在卸载K8s组件前，先执行kubeadm reset命令，清空K8s集群设置
kubeadm reset
卸载管理组件
yum erase -y kubelet kubectl kubeadm kubernetes-cni
删除基础组件镜像。基础组件通过Docker镜像部署，因此只需要强制删除对应镜像即可卸载。
docker rmi -f registry.cn-hangzhou.aliyuncs.com/google_containers/kube-proxy:v1.15.0
docker rmi -f registry.cn-hangzhou.aliyuncs.com/google_containers/kube-apiserver:v1.15.0
docker rmi -f registry.cn-hangzhou.aliyuncs.com/google_containers/kube-scheduler:v1.15.0
docker rmi -f registry.cn-hangzhou.aliyuncs.com/google_containers/kube-controller-manager:v1.15.0
docker rmi -f registry.cn-hangzhou.aliyuncs.com/google_containers/kube-proxy:v1.14.0
docker rmi -f registry.cn-hangzhou.aliyuncs.com/google_containers/kube-controller-manager:v1.14.0
docker rmi -f registry.cn-hangzhou.aliyuncs.com/google_containers/kube-apiserver:v1.14.0
docker rmi -f registry.cn-hangzhou.aliyuncs.com/google_containers/kube-scheduler:v1.14.0
docker rmi -f registry.cn-hangzhou.aliyuncs.com/google_containers/coredns:1.3.1
docker rmi -f registry.cn-hangzhou.aliyuncs.com/google_containers/etcd:3.3.10
docker rmi -f registry.cn-hangzhou.aliyuncs.com/google_containers/pause:3.1
