[nova][operators] Upcoming change breaking out of tree virt drivers in Nova

Hi, There's a nasty race condition when using the ironic driver with Nova.[0] The patch to fix it[1] adds a use_cache argument to the virt driver's get_info method. This is caught and handled so that we can backport the fix, but a follow-up change on master[2] removes the error handling. You'll need to update your out-of-tree virt drivers, if you have one, to add this argument to work with the Stein release. And if your virt driver caches instance information, it would be worth skipping or refreshing that cache when use_cache=True is passed. Sorry for the inconvenience. :) [0] https://bugs.launchpad.net/nova/+bug/1815791 [1] https://review.openstack.org/#/c/636699 [2] https://review.openstack.org/#/c/640043 // jim