Reset Kubernetes cluster
So yes, basically when you create a single control-plane cluster using kubeadm - you are installing cluster that has single control-plane node, with a single etcd database running on it.
The default etcd directory used by kubeadm is /var/lib/etcd on the control-plane node. You should clean it up to avoid restoring previous cluster configuration.
BTW, there is the same issue for k8s 1.15. And it should be fixed 1.15.1 https://github.com/kubernetes/sig-release/blob/3a3c9f92ef484656f0cb4867f32491777d629952/releases/patch-releases.md#115