Kustomize 2.0+ not compatible with getting started guide

[randomvariable]

/kind bug

What steps did you take and what happened:
[A clear and concise description of what the bug is.]
Related to #549 - alternatives to kustomize/envsubst
Related to #276 - UX improvements.

What did you expect to happen:
Due to security concerns, the use of commands as a secret generator has been removed, but the current user workflow is reliant upon it.

Anything else you would like to add:
[Miscellaneous information that will assist in solving the issue.]

Workflow needs to be fixed to be compatible with Kustomize 2, ideally in a backwards compatible way.

Environment:

• Cluster-api-provider-aws version:
• Kubernetes version: (use kubectl version):
• OS (e.g. from /etc/os-release):

[randomvariable]

/lifecycle active

[detiber]

/milestone v1alpha1
/priority important-longterm

[detiber]

@randomvariable I don't think we need to enforce backwards compatibility. I'm good with making kustomize 2.x a requirement if we can get everything patched up to work.

[vincepri]

Related to kubernetes-sigs/cluster-api#745

[randomvariable]

Yeah, not intending to. As far as the user-facing bits, they won't notice if we're still using an older kustomize inside bazel to generate bare manifests.