Add SolidFire support as a provider for cinder

- Add SolidFire attributes
- Re-organise SAN attributes, to be generic and import from
  SolidFire/storwize
- Add tests for SolidFire attributes/settings

Implements: blueprint solidfire-cinder-provider
Change-Id: Ic91be41ca04426e829a68a66317d34db08e60b6f
Merge "Add SolidFire support as a provider for cinder"