tipc: fix a slab object leak

When remove TIPC module, there is a warning to remind us that a slab
object is leaked like:

root@localhost:~# rmmod tipc
[   19.056226] =============================================================================
[   19.057549] BUG TIPC (Not tainted): Objects remaining in TIPC on kmem_cache_close()
[   19.058736] -----------------------------------------------------------------------------
[   19.058736]
[   19.060287] INFO: Slab 0xffffea0000519a00 objects=23 used=1 fp=0xffff880014668b00 flags=0x100000000004080
[   19.061915] INFO: Object 0xffff880014668000 @offset=0
[   19.062717] kmem_cache_destroy TIPC: Slab cache still has objects

This is because the listening socket of TIPC topology server is not
closed before TIPC proto handler is unregistered with proto_unregister().
However, as the socket is closed in tipc_exit_net() which is called by
unregister_pernet_subsys() during unregistering TIPC namespace operation,
the warning can be eliminated if calling unregister_pernet_subsys() is
moved before calling proto_unregister().

Fixes: e05b31f4 ("tipc: make tipc socket support net namespace")
Reviewed-by: Erik Hugne <erik.hugne@ericsson.com>
Signed-off-by: Ying Xue <ying.xue@windriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/tipc/core.c

@@ -152,11 +152,11 @@ static int __init tipc_init(void)
 static void __exit tipc_exit(void)
 {
 	tipc_bearer_cleanup();
+	unregister_pernet_subsys(&tipc_net_ops);
 	tipc_netlink_stop();
 	tipc_netlink_compat_stop();
 	tipc_socket_stop();
 	tipc_unregister_sysctl();
-	unregister_pernet_subsys(&tipc_net_ops);
 
 	pr_info("Deactivated\n");
 }