Create and attach other required openstack resources
Rather than expecting a user to create keypair prior to run
infra-ansible, just make infra-ansible to create the keypair
per the variable passed as keypair_contents on infra_config.yml.
Role provision_infra_servers not only creates instances, but also
volumes and now kepairs, thus also renaming the provision_infra_servers
role and playbook to setup_openstack_resources.
Rather than relying on system-wide packages, just
create the virtualenv and leverage the already available
requirements.txt, which installs ansible along with other
Also pull the openstack inventory in the local inventory folder
as ansible pip package does not bundle the inventory utility.