volume/api: specify a default backend

When using multi-backend in Cinder, we need to specify a default type to
avoid any error when creating a volume without specifying a type.

This patch is backward compatible when not using multi-backend and make
the catalog fail if we don't specify the value.

Also, it updates puppet-cinder to last stable/havana commit.

Signed-off-by: Emilien Macchi <emilien.macchi@enovance.com>
Merge pull request #395 from enovance/feature/394/emilien

volume/api: specify a default backend