Default cinder enable_v1_api to true

As of Juno, Cinder will be deprecating the Cinder V1 API and setting it
to not be enabled by default. We'll make it enabled in devstack to
continue tests while it's supported.

Change-Id: Ia09eed0375a73c69a29b1aa379b5bd9fd3a1f5b7
Merge "Default cinder enable_v1_api to true"