OpenStack Infra has jobs to run this on both Ubuntu Trusty and CentOS7.
* Add minitest to Gemfile (dependency to run beaker on centos - see
http://projects.theforeman.org/issues/2650 for details)
* separate nodepool files to have trusty & centos7 support in OS infra
* basic_swift_spec: add case for repo configuration and support
RH systems.
Change-Id: I745fa76b2b36b0dbada83260fedffc4ee60f9c03
Closes-bug: #1444736