Operator-sdk: Expose the k8s_client

[matyix]

The operator-sdk library allows CRUD operations on K8S resources through the actions and query packages. There might be cases when it is desired to build custom business logic that requires access to the k8s_client (access to the k8s api server). The SDK might expose the k8s_client as well.

[allamand]

I would like to access the k8s_client from the sdk to be able to exec into some pods to execute commands and get results.

[saada]

It would be great to also have an example in the docs to exec into a pod using the exposed client.