Change the devstack image to the default Atomic 23 image.
Update templates not to rely on interface naming because the names
changed between Atomic 21 and Atomic 23 images.
Add a functional test to validate minion node registration.
Update docs to refer to a generic Atomic image.
Co-Authored-By: Hongbin Lu <hongbin.lu@huawei.com>
Implements: blueprint atomic23
Change-Id: Id67244e3f452b3c7c3c46fdabcca3a5c141a76c0