Switch Nova to the Cinder v2 API

As of commit bc516eb0178ec2ecee3c7f55f7400326bec8ec09 Nova
now defaults to the Cinder V2 API.

Once we land Ic20d8df1d7bb559f6a2fe76f35c2e419477604eb we
should once again be able to make use of the default Nova
setting in TripleO again.

Change-Id: I0e5499c0850c1bb9d72aaa68e2e4d5ba2fc56375
Closes-bug: #1391603
Merge "Switch Nova to the Cinder v2 API"