Code review comment for lp://qastaging/~danilo/maas/bug-1688060-houdini-pod-nodes

lgtm! I think this would prevent any machine that was part of the pod and became something else to be recommissioned if refreshed.

The one thing in the future is that we will have to show it there with a different status. But that's a future thing.

Since Newell/Blake worked on RSD, I'd like a review from either of them before landing.