See https://bugzilla.redhat.com/show_bug.cgi?id=1240687

Returning 0 from a configfs store function results in infinite retries.
Reported-by: Yanko Kaneti <yaneti@declera.com>
Signed-off-by: Andy Grover <agrover@redhat.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>