Glance caching updates to support keystone service tenants:
* Update glance-cache-manage so that it supports the same style OS_
environment variables and CLI options for auth that bin/glance does.
* Updates registry/client so that it supports Keystone KSL style
service tenants. As services no longer use admin_tokens this is
a requirement to be able to use caching w/ KSL.
Fixes LP Bug #949486.
Change-Id: I8d0e56a9ec0d20ef56ed2ce8b860d987ae159e01