CVE-2015-7560: s3: smbd: Refuse to set an ACL from a POSIX file handle on a symlink.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=11648

Signed-off-by: Jeremy Allison <jra@samba.org>
Reviewed-by: Michael Adam <obnox@samba.org>
