New Cinder volume driver for openvstorage

New Cinder volume driver for openvstorage

Open vStorage is an open-source software defined storage VM storage
router, a layer in between Virtual machines and storage backends.
It is compatible with Swift (via S3) interface as backend and nova
compute nodes as frontend, it serves volumes via a virtual filesystem
 using .raw files. Multiple Storage Routers can coordinate between
them and allow live migration with near-zero copy (only local cache
is synced).
The driver implements basic volume operations (create, delete,
snapshot,clone volume, clone snapshot, create from image, upload to
 image).

Implements: blueprint open-vstorage-volume-driver
Change-Id: I4a195aacb34fb1300c158c2d8163887b913b6de8