Fix signature could not be verified for kubernetes

[luk4z7]

Changed the shell script on installation of the
kubelet, kubeadm to sync with documentation

https://github.com/kubernetes/kubernetes/issues/60134 https://kubernetes.io/docs/setup/production-environment/tools/kubeadm/install-kubeadm/#installing-kubeadm-kubelet-and-kubectl

[scholzj]

Thanks for the PR.