kubeadm offline installer support

[helphi]

We hope kubeadm can support offline installer such as kubectl and minikube, because we can't access google cloud in China.

For example, i can download minikube from https://github.com/kubernetes/minikube/releases, and then put it in /usr/local/bin, but i can't download kubeadm from somewhere because it is in google cloud apt/yum repository.

/kind feature
/area kubeadm

[fabriziopandini]

@helphi kubeadm binaries are available https://dl.k8s.io/release/{release}/bin/linux/amd64/kubeadm
release are semantic version strings with v prefix e.g. ´v1.8.0or labels likelatest, ´stable

[luxas]

@helphi This is documented on the website: https://kubernetes.io/docs/admin/kubeadm/#running-kubeadm-without-an-internet-connection

[jimangel]

If anyone comes across this post, looks like the link changed: https://kubernetes.io/docs/reference/setup-tools/kubeadm/kubeadm-init/#running-kubeadm-without-an-internet-connection