Exercises use nova volume-* commands still. This works fine,
however moving forward now that cinder is the default volume service
we should use the cinderclient explicitly for the applicable calls.
Attach/Detach are still novaclient commands, however the others
(create, delete, list, etc) should be cinderclient.
Change-Id: I336de1b69a32eee6c91655b0a5bf8541b243f2f0