Add Region and Multiples into default globals.yml

Currently, the documentation around configuring regions directs
you to make changes to openstack_region_name and multiple_regions_names
in the globals.yml file.
The defaults weren't represented in there which could potentially cause
confusion. This change adds these defaults with a brief description.

TrivialFix

Change-Id: Ie0ff7e3dfb9a9355a9c9dbaf27151d90162806dd