openshift/installer: Bootstrap nodes allow anonymous authentication on kubelet port 10250

A flaw was found in the OpenShift Installer before version v0.9.0-master.0.20210125200451-95101da940b0. During installation of OpenShift Container Platform 4 clusters, bootstrap nodes are provisioned with anonymous authentication enabled on kubelet port 10250. A remote attacker able to reach this port during installation can make unauthenticated `/exec` requests to execute arbitrary commands within running containers. The highest threat from this vulnerability is to data confidentiality and integrity as well as system availability.