containerd does not support systemd cgroupDriver

[Hua Zhang]

If we want to use cgroupDriver=systemd, we need to do:

1, configure kubelet to use cgroupDriver=systemd

juju config kubernetes-worker kubelet-extra-config="{cgroupDriver: 'systemd'}"

# grep -r 'cgroupDriver' /root/cdk/kubelet/config.yaml
cgroupDriver: systemd

2, configure containerd to use SystemdCgroup = true according to issue [1] and [2].

[plugins."io.containerd.grpc.v1.cri".containerd.runtimes.runc.options]
  SystemdCgroup = true

but containerd charm [3] doesn't support to configure cgroupDriver, so we saw the following issue that memory metric just has one item workingSetBytes.

root@juju-88a257-k8s-4:~# curl -qk -H "Authorization:Bearer $(kubectl -n kube-system get secret metrics-server-token-rtz6s -o jsonpath={.data.token} | base64 -d)" -k https://127.0.0.1:10250/stats/summary 2>/dev/null| jq .pods[0].containers[0].memory
{
  "time": "2021-11-23T03:45:56Z",
  "workingSetBytes": 65458176
}

[1] https://github.com/kubernetes/kubernetes/issues/106514
[2] https://github.com/containerd/containerd/issues/4900
[3] https://github.com/charmed-kubernetes/charm-containerd/blob/master/templates/config.toml