Move to use the openstack-ansible-tests repository for Swift.
Make changes use Ansible 2.1.1 (These are required for gating to work
properly, since the majority of repositories have already changed).
Additionally, lets set this up to work with 1 infra host in the MR swift
gate to improve efficiency.
Change-Id: Ic0d35bcf8bafb90a986c7cdda3987f70580af165