orphaned rule if inserted while policy under deletion

[Eric K]

In multi-policy-engine scenario, if node 1 attempts to insert a rule A into policy X, while node 2 attempts to delete policy X, rule A may remain after policy X deletion.

For example, node 1 may execute this function [1] just after another node finishes executing this for-loop [2].

A proper fix may take some thought. May require the rules table to be locked while the delete_policy function is in progress.

[1] https://github.com/openstack/congress/blob/master/congress/db/db_policy_rules.py#L59
[2] https://github.com/openstack/congress/blob/master/congress/db/db_policy_rules.py#L74

[Eric K (ekcs)]

Retargeting for ocata because this is a low encounter-likelihood bug and the potential fix is non-trivial and of some risk. I'll upload proposed fix sketch for review.

[OpenStack Infra (hudson-openstack)]

Change abandoned by Nate Johnston (<email address hidden>) on branch: master
Review: https://review.opendev.org/375719
Reason: Project retirement