fedora/centos-minimal don't obey DIB_DISTRIBUTION_MIRROR currently. I
don't really want them too -- we want to be able to separate the
mirrors used during the build process from those embedded into the
final image. Add DIB_YUM_MINIMAL_BOOTSTRAP_REPOS which is a directory
with repo files to use during the install.
This introduces setup-gate-mirrors.sh which is intended to setup
repo/sources/whatever files in the openstack gate that point to the
local region mirror. It pulls the info from the mirror_info.sh script
on each CI node.
The openstack-ci-mirrors element is updated to export these variables.
elements are updated to depend on it. Tests are restored
Change-Id: I7604fc4d41cb1483be16b8d628a24e8fc764f515
649f0b66d9