Comment 51 for bug 1596075

Give it another shot with https://review.openstack.org/#/c/339226/9 . I suspect its an error in the policy engine that we aren't seeing.

(BTW, thanks for helping with this. We have quite a few more db contentious operations and compare and swap logic for better consistency but it results in more deadlock risk, especially in galera, so we need to get these cases shaken out)