This patch improves the documentation for Cinder as a backend for
Glance by including:
1. Configuration changes with the New location API
2. Details about how the optimizations are performed vs the generic path
3. Pre-conditions for the optimizations to work
4. Recommendations regarding the internal/service project while uploading volume
Change-Id: I6f3035178b2b43145b34fbeb14bac22d0b52bc27
Signed-off-by: Rajat Dhasmana <rajatdhasmana@gmail.com>