In neutron CI queues we were running tempest-slow-py3 and
tempest-ipv6-only jobs which are defined in tempest repository and runs
all tests, e.g related to Swift or Cinder.
This patch defines new jobs: "neutron-tempest-slow-py3" and
"neutron-tempest-ipv6-only" which inherits from the tempest jobs but
disables Cinder and Swift services.
Additionally "neutron-tempest-ipv6-only" job now runs only
Originally in master branch it was done in patch  but due to
completly different structure of zuul config files in stable/ussuri in
newer branches, there is no point to do regular cherry-pick to
stable/train branch from there. So this patch is doing similar change
but it's valid only for stable/train and older branches.