dlers may be active.

For discussion of userland confusion, see:
http://www.mail-archive.com/bug-coreutils@gnu.org/msg17988.html

This patch corrects the error returns so that ENOTSUP is reported
to userspace as required.

Signed-off-by: James Morris <jmorris@namei.org>
Acked-by:  Stephen Smalley <sds@tycho.nsa.gov>
Acked-by: Serge Hallyn <serue@us.ibm.com>