Suggestion for fixing the exclude nodes filter

[dgem]

Hi,

As per comment from @js-timbirkett, the filtering of nodes via EXCLUDE_NODE_LABEL_KEYS doesn't seem to work.

As a suggestion, I've modified get_k8s_nodes() to return nodes, excluded_nodes , then modified the callers of it, etc.

Also fixes: https://github.com/hellofresh/eks-rolling-update/issues/94

Let me know what you think,

Kind regards Dan