ctdb: remove queue destructor as it isn't needed anymore

ctdb: remove queue destructor as it isn't needed anymore

After

commit e097b7f8ff1a9992de1d11474dac4969e30cd679
Author: David Disseldorp <ddiss@suse.de>
Date:   Sun Jul 31 03:14:54 2011 +0200

    io: Make queue_io_read() safe for reentry

the destructor has no purpose anymore, therfore, remove it.

Signed-off-by: Swen Schillig <swen@vnet.ibm.com>
Reviewed-by: Martin Schwenke <martin@meltin.net>
Reviewed-by: David Disseldorp <ddiss@samba.org>
Autobuild-User(master): Martin Schwenke <martins@samba.org>
Autobuild-Date(master): Mon Aug  6 11:37:32 CEST 2018 on sn-devel-144