This patch implements test scripts intended for use by all
OpenStack-Ansible role tests.
The intent is to simplify the role tox.ini configuration
and ensure that as many changes to role testing configuration
can be managed from the centralised tests repo instead of
individually in each repository.
The common tests repo target location when cloned is changed
from 'tests/playbooks' to 'tests/common' to better reflect
the content and purpose.
Change-Id: I1a93329ada24670c87588ce5a07f92c9bce4e50b
9a09e9ff07