Initial support for a centos7 image.
This is separate to rhel7 because the major differences are things
like repo and image locations, which are always going to be different.
We should merge any real changes into the redhat-common layers.
Apart from the added support files in centos7/*, the other change is
mostly modifications to redhat-common's extract-image to handle
different partition layouts of the centos7 image.
Change-Id: I943abe5ff0a803f36eda266a79af0d9220edcae7
As with the previous similar changes, this is intended to catch
problems as they happen instead of ignoring them and continuing on
to potentially fail later. Setting this on all existing scripts
will allow us to enforce use via Jenkins.
Change-Id: Iad2d490c86dceab148ea9ab08f457c49a5d5352e
Add an element intended for use in both Fedora and RHEL. This
allows them to share install steps that are common to both.
Change-Id: Ie4e820a7b777b8701514351b1f802cfe57c3812e
