Currently there are tasks in kubeadm that aren't idempotent after the control plane is up.
For example, nearly all code that creates resources will fail if there already is such a resource (very common when upgrading for instance.

In order to unblock upgrades; we need to make these tasks idempotent. I and @pipejakob are working on that and have PRs in flight to fix this.

I now spawned this as a sub-task of #278