For external CA users that have prepared the kubeconfig files
for components, they might wish to provide a custom API server URL.
When performing validation on these kubeconfig files, instead of
erroring out on such custom URLs, show a klog Warning.
This allows flexibility around topology setup, where users
wish to make the kubeconfigs point to the ControlPlaneEndpoint instead
of the LocalAPIEndpoint.
Fix validation in ValidateKubeconfigsForExternalCA expecting
all kubeconfig files to use the CPE. The kube-scheduler and
kube-controller-manager now use LAE.
edaef35eac