Comment 1 for bug 1694736

These are only run when ssh validation is enabled, which was made the default in devstack last week:

https://github.com/openstack-dev/devstack/commit/6d302a83242e2e83ca911da9c2c3cd7cb93b789c

That's likely why it's on in the xenproject CI now. You could disable it explicitly until the bug is fixed. I'm not sure why this would cause issues with libvirt+xen but not libvirt+qemu though.