Add "region" config for each service

Added config items are:
    compute.region
    image.region
    network.region
    volume.region
    object_storage.region
    orchestration.region

RestClient decides target endpoints according to these values. If
these values are not set, the value of identity.region is used
instead.

Fixes bug 1210039

Change-Id: If2a01fae2893ee5740a94e97389164eb000538d7
5 files changed