This helps enable a graceful upgrade/downgrade process between 1.6.x and
1.7.x kubeadm clusters (although no guarantees outside of that range) by
doing:
$ kubeadm init --kubernetes-version <version> --skip-preflight-checks
Without this change, the command fails with an error that the node taint
is duplicated.
This is part of https://github.com/kubernetes/kubeadm/issues/278