kubelet: add initial support for cgroupv2

do a conversion from the cgroups v1 limits to cgroups v2.

e.g. cpu.shares on cgroups v1 has a range of [2-262144] while the
equivalent on cgroups v2 is cpu.weight that uses a range [1-10000].

Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>

pkg/kubelet/cm/container_manager_linux.go

@@ -161,6 +161,10 @@ func validateSystemRequirements(mountUtil mount.Interface) (features, error) {
 		return f, fmt.Errorf("%s - %v", localErr, err)
 	}
 
+	if cgroups.IsCgroup2UnifiedMode() {
+		return f, nil
+	}
+
 	expectedCgroups := sets.NewString("cpu", "cpuacct", "cpuset", "memory")
 	for _, mountPoint := range mountPoints {
 		if mountPoint.Type == cgroupMountType {
@@ -884,6 +888,11 @@ func getContainer(pid int) (string, error) {
 		return "", err
 	}
 
+	if cgroups.IsCgroup2UnifiedMode() {
+		c, _ := cgs[""]
+		return c, nil
+	}
+
 	cpu, found := cgs["cpu"]
 	if !found {
 		return "", cgroups.NewNotFoundError("cpu")