The current constraints generation for the
installation involves multiple tasks and multiple
variables.
Using multiple tasks extends the installation time
unnecessarily and the additional variables are
unnecessary.
This patch aims to simplify the mechanism and
hopes to speed it up a little.
The tests/os_keystone-overrides.yml file is removed
as it is unnecessary given the merge of
https://review.openstack.org/381479
Depends-On: I0e6d43a9f22add78f693e8836f1dd852be74d6c5
Change-Id: Ief9c7f124eb58b986192b2f958c971197d410799
c5a0cce3c6