mn/n/kubernetes: fix warnings

This fixes a warning that we do not explicitly set the root cgroup and
one that we specify the container runtime type explicitly; in 1.24
everything other than "remote" has been dropped.

Change-Id: I7beb0fbbbd5e38715b8b1e76dac99d2d7c4275d5
Reviewed-on: https://review.monogon.dev/c/monogon/+/785
Tested-by: Jenkins CI
Reviewed-by: Sergiusz Bazanski <serge@monogon.tech>
diff --git a/metropolis/node/kubernetes/kubelet.go b/metropolis/node/kubernetes/kubelet.go
index 31357ab..c643e91 100644
--- a/metropolis/node/kubernetes/kubelet.go
+++ b/metropolis/node/kubernetes/kubelet.go
@@ -98,6 +98,7 @@
 		HairpinMode:                  "none",
 		MakeIPTablesUtilChains:       reconciler.False(), // We don't have iptables
 		FailSwapOn:                   reconciler.False(), // Our kernel doesn't have swap enabled which breaks Kubelet's detection
+		CgroupRoot:                   "/",
 		KubeReserved: map[string]string{
 			"cpu":    "200m",
 			"memory": "300Mi",
@@ -126,7 +127,6 @@
 	}
 	cmd := exec.CommandContext(ctx, "/kubernetes/bin/kube", "kubelet",
 		fargs.FileOpt("--config", "config.json", configRaw),
-		"--container-runtime=remote",
 		fmt.Sprintf("--container-runtime-endpoint=unix://%s", s.EphemeralDirectory.Containerd.ClientSocket.FullPath()),
 		fmt.Sprintf("--kubeconfig=%s", s.mountKubeconfigPath),
 		fmt.Sprintf("--root-dir=%s", s.KubeletDirectory.FullPath()),