[nova][ci] Hold your rechecks

Due to tooz changing their python support to no longer support py3.8 by the 4.0 version, the Nova functional jobs are now blocked until we either block tooz>=4 in upper-constraints or we completely remove py3.8 support for the CI jobs we run. A proposal already exists : https://review.opendev.org/c/openstack/nova/+/881339 Anyway, hold your rechecks. -Sylvain