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>.
Make kubelet `ReadLogs` backward compatible.
`containerLogPathLabelKey` label was added in dockershim since 1.5. 121a91eb12
ContainerStatus.LogPath was added since Kubernetes 1.7. c3b52267ca
I believe it is safe to reply on this field without backward compatibility issue. And `crictl` is using it as well https://github.com/kubernetes-incubator/cri-tools/blob/master/cmd/crictl/logs.go#L88.
With this change, in the future, kubelet `ReadLogs` will be backward compatible as long as the log format is backward compatible.
@feiskyer @yujuhong @kubernetes/sig-node-pr-reviews
Signed-off-by: Lantao Liu <lantaol@google.com>
**Release note**:
```release-note
none
```
ae53b78971