The Scality volume driver was removed from Cinder in Ocata:
a931f9db79554630d8d71fcff1334bb4e37cb398
It's unmaintained and therefore no longer supported, and won't
even work with recent Cinder, so let's remove it.
Change-Id: I0cfa0c4b3d7138f989225a44bdedfa716a035a14