[sahara][sahara-cores] Combined patch that recovers CI tests

Hi sahara cores, As you might know Sahara has been broken for quite some time now due to multiple reasons, and didn't have passing tests for Zed release at all. I have come up with a patch [1] that fixes major issues, including: * Zuul Queus definition * Adapting new jsonschema version * Replacing usage of iteritems with six As a result Zuul is happy, all tempest and tox tests are passing it the moment. It would be great if you could review these changes and land other important patches to unblock other contributors in the project and prevent it from falling under "inactive" projects list. [1] https://review.opendev.org/c/openstack/sahara/+/864728