Switch to the new canonical constraints URL on master
Switch to the new canonical constraints URL on master

Reference:
1. http://lists.openstack.org/pipermail/openstack-discuss/2019-May/006478.html
2. https://review.opendev.org/#/c/601188

Change-Id: Ifb7bcc88e52dc120070501d531e2889820cdd643

openstack/python-ironicclient,openstack/python-ironicclient