Rename env var <X>_CLI to <X>CLIENT (X=SOLUM/MISTRAL) to make it consistent with contrib/devstack/lib/solum in openstack/solum repo.
Added barbican and python-barbicanclient to the devstack

Enable barbican service in vm/docker environments

Related-Bug: #1319604
Merge pull request #15 from pravisankar/support-private-github

Changes needed for supporting private github repo