[install] Fix package repositories
[install] Fix package repositories

Fix package repositories, particularly for RDO, and
also clarify finalization content.

Change-Id: I7881ec2bc1dc7bcdbda74f96efbbd88daf17b73f
Implements: blueprint installguide-liberty

openstack/openstack-manuals,openstack/openstack-manuals,AlekhyaMallina-Vedams/openstack-manuals,openstack/openstack-manuals,openstack/openstack-manuals,AlekhyaMallina-Vedams/openstack-manuals,AlekhyaMallina-Vedams/openstack-manuals