Unpacker pod is constantly being re-created

[joelanford]

Our diff logic that decides whether or not to replace an unpack pod is not working correctly. When rukpak is deployed in a cluster with a pod mutation webhook that affects the unpack pod, we currently see those unrelated pod mutations as diffs and decide we need to re-create the pod, which results in those same mutations, which results in our re-spinning the pod... and the cycle continues forever.