Use upper constraints for all jobs in tox.ini
Use upper constraints for all jobs in tox.ini

Openstack infra now supports upper constraints for
all jobs. Updated tox.ini to use upper constraints
for all jobs.

Change-Id: I74a511e3d0f5c76506c0505fd9cc980b48b242a5
Closes-Bug: #1614361

openstack/zaqar,openstack/zaqar,openstack/zaqar,openstack/zaqar