Tox is not anymore pre-installed on the OpenDev CI images.
The file package.json needs tox, install it to fix the job.
Install it via a pre-run playbook so that this is run in addition to all
of the playbooks of the parent.
Note for the reviewer in stable/stein we run nodejs-4 jobs as runtime.
I have cherry-pick this change from master which run nodejs-10 job
but simliar changes fixes the nodejs-4 jobs So I have added pre-run
playbook for nodejs-4 job as well.
(cherry picked from commit