Comment 26 for bug 1491131

Notes:

Could be related, but wasn't available in Kilo, where shihanzhang hasn't seen it (check log stash for occurrences in kilo):

https://review.openstack.org/#/c/187483/

Not likely to fix this bug but worth backporting because of their own bugs:

https://review.openstack.org/#/c/187433/4 : https://launchpad.net/bugs/1458786

https://review.openstack.org/#/c/177159/16 : https://launchpad.net/bugs/1448022

Not likely to fix this, but may be lower priority (this only leaves unused ipsets on the system, but does not break the agent):

https://review.openstack.org/#/c/190991/