Refactor of linting/config validation

* Use the built-in pykwalify cli validator
* Use set -e on loop inside tox.ini to ensure invalid configs fail CI

Change-Id: I251f7ead8393b97e93de03dc3b6accbdd9670092

conf/browbeat-workloads.yml

@@ -3,7 +3,6 @@ browbeat:
   results: results/
   rerun: 1
   cloud_name: openstack
-  overcloud_credentials: /home/stack/overcloudrc
 elasticsearch:
   enabled: false
   regather: false