Start using status.hostIP in k8s daemonsets examples

First reported by @dlaidlaw.

As of Kubernetes 1.7 (kubernetes/kubernetes#42717), we can now retrieve the host IP directly from the downward API via the `status.hostIP` field, without needing to rely on the `spec.nodeName` field, which isn't addressable in all Kubernetes environments (including minikube -- #130).

We should update our example configs in this repo to start using `status.hostIP` instead of `spec.nodeName`, but we also need to figure out a way to ensure backwards compatibility with older versions of Kubernetes, either by versioning the config files or doing something smarter with environment variable fallback.

Inspect the repository's example configs to find uses of `spec.nodeName`, then review the Kubernetes downward API support for `status.hostIP` and the older versions that must remain compatible. Decide whether versioned configs or an environment-variable fallback is appropriate, and verify that the daemonset examples work across the supported Kubernetes versions.

Written by the indexing model from the issue text.