python-samba-tool fsmo: Do not give an error on a successful role transfer

python-samba-tool fsmo: Do not give an error on a successful role transfer

Bug: https://bugzilla.samba.org/show_bug.cgi?id=9461

Signed-off-by: Andrew Bartlett <abartlet@samba.org>
Reviewed-by: Stefan Metzmacher <metze@samba.org>
Autobuild-User(master): Stefan Metzmacher <metze@samba.org>
Autobuild-Date(master): Mon Sep 23 12:00:24 CEST 2013 on sn-devel-104
(cherry picked from commit 8d8872ae0a19786452c3be044757b16814b82be8)

Autobuild-User(v4-1-test): Karolin Seeger <kseeger@samba.org>
Autobuild-Date(v4-1-test): Wed Sep 25 10:47:35 CEST 2013 on sn-devel-104