Fix Flatcar Linux docker driver and add cgroups v2

* Remove `/sys/fs/cgroup/systemd` mount since Flatcar Linux
uses cgroups v2
* Flatcar Linux's `docker` switched from the `cgroupfs` to
`systemd` driver without notice

aws/flatcar-linux/kubernetes/workers/cl/worker.yaml

@@ -51,8 +51,7 @@ systemd:
           -v /usr/lib/os-release:/etc/os-release:ro \
           -v /lib/modules:/lib/modules:ro \
           -v /run:/run \
-          -v /sys/fs/cgroup:/sys/fs/cgroup:ro \
-          -v /sys/fs/cgroup/systemd:/sys/fs/cgroup/systemd \
+          -v /sys/fs/cgroup:/sys/fs/cgroup \
           -v /var/lib/calico:/var/lib/calico:ro \
           -v /var/lib/docker:/var/lib/docker \
           -v /var/lib/kubelet:/var/lib/kubelet:rshared \
@@ -63,6 +62,7 @@ systemd:
           --authentication-token-webhook \
           --authorization-mode=Webhook \
           --bootstrap-kubeconfig=/etc/kubernetes/kubeconfig \
+          --cgroup-driver=systemd \
           --client-ca-file=/etc/kubernetes/ca.crt \
           --cluster_dns=${cluster_dns_service_ip} \
           --cluster_domain=${cluster_domain_suffix} \