Notes on enabling consistency groups in devstack:
http://docs.openstack.org/admin-guide/blockstorage-consistency-groups.html
You'll also need to modify the local cinder policy file.
Though that's not actually enough to make it work since
devstack only provides the LVM volume type and CGs don't
work with LVM. You can attempt to create CGs, but they
will error.
Change-Id: I0ab541c81570cd5f67bb7d04c01bc92bc5cc3ab5
Implements: blueprint reorganise-volumes
f85e0ffa91