Clients for various OpenStack services
were updated so that it would be
possible to specify region name explicitly.
If it is not provided then for clients that are
used internally by the core library it is taken
from the current region. Otherwise the default
environment region is used.
Change-Id: I289c7f8dc93a30ba1d5aa06d9da29a6af1308b9a
acd269f9b2