libcli/smb: don't overwrite status code

libcli/smb: don't overwrite status code

The original commit c5cd22b5bbce724dcd68fe94320382b3f772cabf from bug
9175 never worked, as the preceeding signing check overwrote the status
variable.

Bug: https://bugzilla.samba.org/show_bug.cgi?id=9175

Signed-off-by: Ralph Boehme <slow@samba.org>
Reviewed-by: Stefan Metzmacher <metze@samba.org>
Autobuild-User(master): Ralph Böhme <slow@samba.org>
Autobuild-Date(master): Tue Nov 13 17:28:45 CET 2018 on sn-devel-144

(cherry picked from commit 5a8583ed701be97c33a20b2a20f6bbb8ac2f8e99)