Comment 11 for bug 1493512

I remember that https://review.openstack.org/#/c/91722/ introduced some upgrade issue in Kilo such that you couldn't upgrade from juno to kilo in some cases, I can't remember what exactly now, dansmith would remember since I think he fixed it.

https://review.openstack.org/#/c/108468/ was a related change after https://review.openstack.org/#/c/91722/ because it broke live migration with NFS.