Add kubeconfig's for kube-scheduler and kube-controller-manager

* Generate TLS client certificates for `kube-scheduler` and
`kube-controller-manager` with `system:kube-scheduler` and
`system:kube-controller-manager` CNs
* Template separate kubeconfigs for kube-scheduler and
kube-controller manager (`scheduler.conf` and
`controller-manager.conf`). Rename admin for clarity
* Before v1.16.0, Typhoon scheduled a self-hosted control
plane, which allowed the steady-state kube-scheduler and
kube-controller-manager to use a scoped ServiceAccount.
With a static pod control plane, separate CN TLS client
certificates are the nearest equiv.
* https://kubernetes.io/docs/setup/best-practices/certificates/
* Remove unused Kubelet certificate, TLS bootstrap is used
instead

aws/flatcar-linux/kubernetes/bootstrap.tf

@@ -1,6 +1,6 @@
 # Kubernetes assets (kubeconfig, manifests)
 module "bootstrap" {
-  source = "git::https://github.com/poseidon/terraform-render-bootstrap.git?ref=19c3ce61bd32801bef791e4848b2a3eac1b758c8"
+  source = "git::https://github.com/poseidon/terraform-render-bootstrap.git?ref=ac5cb9577408cba65f66b0ce35a8881c3ca5d63b"
 
   cluster_name          = var.cluster_name
   api_servers           = [format("%s.%s", var.cluster_name, var.dns_zone)]

aws/flatcar-linux/kubernetes/cl/controller.yaml

@@ -155,7 +155,7 @@ storage:
           chown -R etcd:etcd /etc/ssl/etcd
           chmod -R 500 /etc/ssl/etcd
           chmod -R 700 /var/lib/etcd
-          mv auth/kubeconfig /etc/kubernetes/bootstrap-secrets/
+          mv auth/* /etc/kubernetes/bootstrap-secrets/
           mv tls/k8s/* /etc/kubernetes/bootstrap-secrets/
           mkdir -p /etc/kubernetes/manifests
           mv static-manifests/* /etc/kubernetes/manifests/
@@ -169,7 +169,7 @@ storage:
       contents:
         inline: |
           #!/bin/bash -e
-          export KUBECONFIG=/etc/kubernetes/secrets/kubeconfig
+          export KUBECONFIG=/etc/kubernetes/secrets/admin.conf
           until kubectl version; do
             echo "Waiting for static pod control plane"
             sleep 5