Support new k8s Versions

[phenixblue]

What type of PR is this?

Uncomment only one /kind <> line, hit enter to put that in a new line, and remove leading whitespace from that line:

/kind bug
/kind cleanup
/kind deprecation
/kind design
/kind documentation

/kind feature

/kind release

What this PR does / why we need it:

Adjusts the init code to support new K8s API versions for certificates and such. This enabled support for newer k8s versions (v1.21+).

Which issue(s) this PR fixes:

Fixes #57

Special notes for your reviewer:

Picks up where #65 left off

Does this PR introduce a user-facing change?:

Additional documentation e.g., usage docs, etc.:

- [Usage]: README.md
- [Kubernetes CSR]: https://kubernetes.io/docs/reference/access-authn-authz/certificate-signing-requests
- [Kubernetes API Migration]: https://kubernetes.io/docs/reference/using-api/deprecation-guide/#lease-v122
- [EKS CSR]: https://docs.aws.amazon.com/eks/latest/userguide/cert-signing.html

[ilrudie]

Left a couple of non-blocking comments/questions but I think it's good to go if you don't care to address those in this MR so I'll go ahead and approve now.

[ilrudie]

LGTM