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 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.
