bug: fix node eviction when scaling down.

[jmcgrath207]

Fixes https://github.com/jmcgrath207/k8s-ephemeral-storage-metrics/issues/64

There was a bug where nodes were not being evicted when scaling down.

This change also includes:

• Scale up and down e2e test
• Fixed flakiness on the minikube registry
• refactor for grow and shrink e2e test.