ctdb-mutex: Fix CID 1359217 Resource leak (RESOURCE_LEAK)

Signed-off-by: Martin Schwenke <martin@meltin.net>
Reviewed-by: Amitay Isaacs <amitay@gmail.com>

Autobuild-User(master): Amitay Isaacs <amitay@samba.org>
Autobuild-Date(master): Wed Aug  3 09:13:55 CEST 2016 on sn-devel-144
