package apt-transport-https should be installed

Ubuntu default install not include apt-transport-https. so if you want to download package from https repo, you need install apt-transport-https package first

docs/getting-started-guides/kubeadm.md

@@ -69,6 +69,7 @@ For each host in turn:
 * SSH into the machine and become `root` if you are not already (for example, run `sudo su -`).
 * If the machine is running Ubuntu or HypriotOS, run:
 
+      apt-get update && apt-get install -y apt-transport-https
       curl -s https://packages.cloud.google.com/apt/doc/apt-key.gpg | apt-key add -
       cat <<EOF > /etc/apt/sources.list.d/kubernetes.list
       deb http://apt.kubernetes.io/ kubernetes-xenial main