Updated openstack/openstack
Project: openstack-dev/devstack  4e10843812a25dd3645bf25f166d9be20ce242a0

Install dib from pip

diskimage-builder makes releases to PyPI and is not part of the
integrated release. Since it's not, we don't need to consume its
master branch - rather, we can consume its releases.

Change-Id: If9297a28604612140c39dfe44e77107d1372f0bb