Use cinder API v2, remove support for v1

Cinder API v1 was deprecated in Juno and is being removed in Kilo.

Implements: blueprint horizon-cinder-v2-preferred-version
Closes-Bug: 1376424
Change-Id: I9bbdf1753a06d33b441a85ff448f475545eafc80
Merge "Use cinder API v2, remove support for v1"