s3: smbd: Fix memory leak in vfswrap_getwd()

s3: smbd: Fix memory leak in vfswrap_getwd()

BUG: https://bugzilla.samba.org/show_bug.cgi?id=13372

Signed-off-by: Andrew Walker <awalker@ixsystems.com>.
Reviewed-by: Jeremy Allison <jra@samba.org>
Reviewed-by: Ralph Boehme <slow@samba.org>
Autobuild-User(master): Jeremy Allison <jra@samba.org>
Autobuild-Date(master): Mon Apr  9 21:48:12 CEST 2018 on sn-devel-144

(cherry picked from commit 461a1172ff819692aa0a2dc5ce7fc5379c8a529e)

Autobuild-User(v4-7-test): Karolin Seeger <kseeger@samba.org>
Autobuild-Date(v4-7-test): Tue Apr 10 14:09:46 CEST 2018 on sn-devel-144