[Tempest] Use Ansible built-in pip to install
[Tempest] Use Ansible built-in pip to install

.. instead of downstream script wrapping venv

Pip is idempotent, so remove "when" flags

Change-Id: I0693fe5522adaf956ab4363a5e04e7f5a43e6341

okolisny/InfraRed,okolisny/InfraRed,redhat-openstack/infrared,okolisny/InfraRed,redhat-openstack/infrared,redhat-openstack/infrared