Updated openstack/openstack
Project: openstack-dev/devstack  31f7475baffcca2742201918c8f3fe7b682c2193
null
cache the pip tarball

there is no need to download the pip tarball over and over again
on rerun. Use the cached value.

Change-Id: Ibcc1807ba2aca062f69839212f05ac9394db9448