While we can specify keystone region where all keystone resources
are created, currently we don't set the specified region correctly
in credential configurations used for authtoken middleware.
Configure region parameter for authtoken according to the parameter
KeystoneRegion so that we're consistent about the region where
we expect to have service users created.
Change-Id: Icc0ee9a859c2c67cae92339c6b4102946150269f