Fix unit suffix and add no_suffix option.

Fix unit suffix and add no_suffix option.

In Cinder we've been using gibibytes, however
we have code in some places using Gigabytes, the brick
LVM code was one of those places.

This change sets the default suffix to gibibytes/mibibytes (1024 based)
and also provides an option to omit the suffix from the response now
that we can say that we're consistent in what is expected.

Change-Id: Id6274ba732bbdf484c5544e005155aebd68eaf2f