[ovn] Use ubuntu minimal as advanced image

Current kernel in Ubuntu focal minimal image
is 5.4.0-1082-kvm and that includes the fix for
missing multicast feature[1], let's use the
minimal image in ovn jobs too like other scenario
jobs[2].

Cannot use minimal image in releases before victoria
as those are pinned to neutron-tempest-plugin-1.6.0
and the required patch [3] is only available since
1.8.0. victoria jobs already have advanced image
specific overrides, added overrides in ussuri ovn job.

[1] https://bugs.launchpad.net/cloud-images/+bug/1946672
[2] https://review.opendev.org/c/openstack/neutron-tempest-plugin/+/813195
[3] https://review.opendev.org/c/openstack/neutron-tempest-plugin/+/813195

Related-Bug: #1948804
Change-Id: Ibe180fc6d1785682033886faf8ba03323bb1a3e8
2 files changed