s3-winexe: Fix winexe core dump (use-after-free)

BUG: https://bugzilla.samba.org/show_bug.cgi?id=14893

Guenther

Signed-off-by: Guenther Deschner <gd@samba.org>
Reviewed-by: Andreas Schneider <asn@samba.org>

Autobuild-User(master): Günther Deschner <gd@samba.org>
Autobuild-Date(master): Fri Nov  5 11:43:57 UTC 2021 on sn-devel-184
