Stop using kubeadm to update server in kubeconfigs (#7338)

Using `kubeadm init phase kubeconfig all` breaks kubelet client certificate rotation
as we are missing `kubeadm init phase kubelet-finalize all` to point to `kubelet-client-current.pem`

kubeconfig format is stable so let's just use lineinfile,
this will avoid other future breakage

This revert to the logic before 6fe22483

Signed-off-by: Etienne Champetier <e.champetier@ateme.com>