kubernetes mixin should allow uninstall step to succeed when resources are not found

[jarnfast]

Synopsis

In the uninstall action the kubernetes mixin should be able to handle situations where resources are not found in a graceful manner.

Reasoning

Attempting to recover from a failed bundle installation using uninstall can be almost impossible. If the step creating the k8s resource hasn't been executed the uninstall of said resources will fail hard.

Proposed solution

Add a boolean ignore-not-found property to the uninstall step that adds --ignore-not-found=<value> to the executed command.
That would allow users of the mixin to have uninstall steps that will succeed even if the resource is gone (or have never been there)