Allow using Flatcar Linux edge on Azure

* Set Kubelet cgroup driver to systemd when Flatcar Linux edge
is chosen

Note: Typhoon module status assumes use of the stable variant of
an OS channel/stream. Its possible to use earlier variants and
those are sometimes tested or developed against, but stable is
the recommendation

azure/container-linux/kubernetes/workers/cl/worker.yaml

@@ -26,6 +26,7 @@ systemd:
         Wants=rpc-statd.service
         [Service]
         Environment=KUBELET_IMAGE=docker://quay.io/poseidon/kubelet:v1.18.5
+        Environment=KUBELET_CGROUP_DRIVER=${cgroup_driver}
         ExecStartPre=/bin/mkdir -p /etc/kubernetes/cni/net.d
         ExecStartPre=/bin/mkdir -p /etc/kubernetes/manifests
         ExecStartPre=/bin/mkdir -p /opt/cni/bin
@@ -69,6 +70,7 @@ systemd:
           --authentication-token-webhook \
           --authorization-mode=Webhook \
           --bootstrap-kubeconfig=/etc/kubernetes/kubeconfig \
+          --cgroup-driver=$${KUBELET_CGROUP_DRIVER} \
           --client-ca-file=/etc/kubernetes/ca.crt \
           --cluster_dns=${cluster_dns_service_ip} \
           --cluster_domain=${cluster_domain_suffix} \