https://git.openstack.org/cgit/openstack/
openstack-ansible-os_tempest/tree/tasks/tempest_run.yml#n24
Syntex is correct, but --serial flag was not getting exposed in
rocky/master os_tempest tempest_run playbook, It refactors
the shell script and nicer so that it works perfectly.
openSUSE 42.3 testing is also removed since 42.3 is almost EOL and
building LXC containers is broken.
Change-Id: Ieca5103f803778a44bbb517954b56a9069babbdd
(cherry picked from commit 8794a6641b)
e30bd4e936