Use GB instead of GiB

Get rid of the annoying difference between what Docker sets as a
Gig for a volume and what we were setting.

So now instead of "docker volume create -0 size 5" giving you a
volume of 5.4GB in the SF UI, you actually see 5 which is what
you want.

daemon/driver.go

@@ -185,7 +185,7 @@ func (d SolidFireDriver) Create(r volume.Request) volume.Response {
 	if r.Options["size"] != "" {
 		s, _ := strconv.ParseInt(r.Options["size"], 10, 64)
 		log.Info("Received size request in Create: ", s)
-		vsz = int64(units.GiB) * s
+		vsz = int64(units.GB) * s
 	} else {
 		// NOTE(jdg): We need to cleanup the conversions and such when we read
 		// in from the config file, it's sort of ugly.  BUT, just remember that