Automatic merge from submit-queue. If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.
fix network value for stats summary for multiple network interfaces
This PR is part of [Heapster #1788](https://github.com/kubernetes/heapster/pull/1788).
The original reason is when there are more than one none `lo`, `docker0`, `veth` network interfaces instead of just one `eth0`, the network interface value is only partial and does not correct. For now, summary stats api only gets the eth0 network interface values.
The original issues about this can be find in [Heapster #1058](https://github.com/kubernetes/heapster/issues/1058) and [Cadvisor #1593](https://github.com/google/cadvisor/issues/1593).
```release-note
Fix stats summary network value when multiple network interfaces are available.
```
/cc @DirectXMan12 @piosz @xiangpengzhao @vishh @timstclair
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
This PR adds pod-level ephemeral storage metric into Summary API.
Pod-level ephemeral storage usage is the sum of all containers and local
ephemeral volume including EmptyDir (if not backed up by memory or
hugepages), configueMap, and downwardAPI.
For pod volumes that reference a PVC, add a PVCRef to the corresponding
volume stat. This allows metrics to be indexed/queried by PVC name
which is more user-friendly than Pod reference
