Add temporary Ansible keystone modules

Due to the licensing issues and the modules not existing in upstream
Ansible yet, I have written a simple module to fill the gaps.

This also uses Keystone v2.0 for all create of users, roles and
endpoints. The implementation of Keystone v3 must be discussed after the
new modules arrive.

Partially-Implements: blueprint ansible-service

Change-Id: I389edd56741360dd26fbbc0a982f365ca27ff446