CVE-2015-5252: s3: smbd: Fix symlink verification (file access outside the share).

Ensure matching component ends in '/' or '\0'.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=11395

Signed-off-by: Jeremy Allison <jra@samba.org>
Reviewed-by: Volker Lendecke <vl@samba.org>
