DIB was retrieving the oldest cloud image file which, presently, means
retrieving CentOS 8.1 instead of CentOS 8.2. Even though DIB runs a
system update and so catches up to latest, this takes bandwidth, time
and final image space (8.1 + system update = 765M qcow2, vs 8.2 + system
update = 518M qcow2).
This patch fixes that by taking the first image name in a descending
order list.
Change-Id: I648fe19f1f76c03c97492b6ac7be6381f6f9261b
* Add "centos" element, a CentOS version-independent element. This is in
line with the same work done for RHEL in Stein cycle.
* Deprecate the centos7 element. CentOS 7 support itself it not
deprecated though. The new "centos" element provides the same support
level as the "centos7" element.
* Add functional testing
The default CentOS version is 8. You can adjust it using the DIB_RELEASE
environment variable.
Change-Id: I373ba2296c4613765676e59aabd9c651345298d1
