xci: infra: bifrost: Avoid installing Ansible twice

xci: infra: bifrost: Avoid installing Ansible twice

We already install Ansible globally and we also install another version
of it in the bifrost venv. Even though the OSA Ansible may move faster
than the bifrost one, we normally pin both projects so we can move them
when they can work with the same Ansible version. As such, lets make the
deployment a little bit faster by simply not installing Ansible twice.

Change-Id: I121ef5979607b62e76300db1bc6d51fc27362d5b
Signed-off-by: Markos Chandras <mchandras@suse.de>