Automatic merge from submit-queue (batch tested with PRs 41844, 41803, 39116, 41129, 41240)
Cleanup client example
**What this PR does / why we need it**:
- Package level `config` variable in `third-party-resources/main.go` is not used, it is shadowed by the one defined in `main()`. Should probably be deleted.
- Package level `kubeconfig ` variable in `out-of-cluster/main.go` is global - make it private to `main()`.
**Which issue this PR fixes**
This fixes https://github.com/kubernetes/client-go/issues/59, except the part about global `api.Scheme`, also adds test with interface check. Supersedes https://github.com/kubernetes/client-go/pull/61.
**Special notes for your reviewer**:
This is my first PR to Kubernetes :)
e1b174842a