Add support for basic multiple regions, that is to say, many OpenStack
with a shared Keystone (same users) and Horizon. The shared Keystone
and Horizon are deployed into one region, for instance RegionOne.
Services of other regions have an access to this Keystone. This
support assumes that the operator knows the name of all OpenStack
regions in advance, and considers as many Kolla runs as there are
regions.

The new variable, multiple_regions_names, contains the name of
regions. It is needed by the region that includes Keystone and
Horizon. In register.yml, it specifies to create as many Keystone
endpoints as there are regiones, so that services of other regions can
connect to Keystone. In local_settings.j2, it changes the render to
support multiple regions in Horizon. The multi-regions.rst explains
how to perform a multiple regions deployment.

Implements: blueprint multi-kolla-config
Change-Id: Icab2aebfc4de0e3bc609950956e0af397705f403