Add pod-level metric for CPU and memory stats

This PR adds the pod-level metrics for CPU and memory stats. cAdvisor
can get all pod cgroup information so we can add this pod-level CPU and
memory stats information from the corresponding pod cgroup

pkg/kubelet/cm/helpers_linux.go

@@ -26,6 +26,7 @@ import (
 	libcontainercgroups "github.com/opencontainers/runc/libcontainer/cgroups"
 
 	"k8s.io/api/core/v1"
+	"k8s.io/apimachinery/pkg/types"
 	"k8s.io/kubernetes/pkg/api/v1/resource"
 	v1helper "k8s.io/kubernetes/pkg/apis/core/v1/helper"
 	v1qos "k8s.io/kubernetes/pkg/apis/core/v1/helper/qos"
@@ -222,3 +223,8 @@ func getCgroupProcs(dir string) ([]int, error) {
 	}
 	return out, nil
 }
+
+// GetPodCgroupNameSuffix returns the last element of the pod CgroupName identifier
+func GetPodCgroupNameSuffix(podUID types.UID) string {
+	return podCgroupNamePrefix + string(podUID)
+}