The 'image create' operation is actually one of two operations: it can
be either an image service (glance) operation if the '--volume' argument
is *not* passed or a block storage (cinder) operation if it is. Make
this clearer and add a log warning users about options that are
supported by the former but not the latter.
Change-Id: Id153c951a7d18403568bf67e13d5e0a4827428d4
Signed-off-by: Stephen Finucane <sfinucan@redhat.com>