Stephen O'Donnell

I think this change looks good in concept. If the comments from @ivandika3 are addressed it should be good to commit. A unit test would be nice too, but I...

My first thought on this, is that if the placement policy already excludes decommissioning nodes via the `isValidateNode` method at the end, could we simply add all decommissioning nodes (and...

But it is wrong for the placement policy to return a decommissioning node. It does indeed filter out any decommission nodes it finds and retries. So it is "removing them"...

I think there are other places in the code where the placement policies are called too. Eg pipeline creation, which could run into the same sort of problems I think....