plexes_used and volumes_used. Now these fields are only informative,
and the <object>_allocated count is used for searches, etc. This also
required checking the object state before doing things with the
presumed object.
Problems-reported-by: Kiril Mitev <kiril@ideaglobal.com>
VINUM_<object>CONFIG: return ENXIO rather than EFAULT if an object
doesn't exist.