Comment 2 for bug 1737395

W/o proper investigation yet, I suspect this might be due to hashring in nova computes is being rebalanced when we stop/restart a compute - a given compute sees the "new" nodes (that were handled by a stopped one) and tries to register them in placement but they are already there as they were registered by the old compute..

But again, this is just an idea to investigate as I might be totally wrong.