l2tp: don't close sessions in l2tp_tunnel_destruct()

Sessions are already removed by the proto ->destroy() handlers, and
since commit f3c66d4e ("l2tp: prevent creation of sessions on terminated tunnels"),
we're guaranteed that no new session can be created afterwards.

Furthermore, l2tp_tunnel_closeall() can sleep when there are sessions
left to close. So we really shouldn't call it in a ->sk_destruct()
handler, as it can be used from atomic context.
Signed-off-by: Guillaume Nault <g.nault@alphalink.fr>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/l2tp/l2tp_core.c

@@ -1246,8 +1246,6 @@ static void l2tp_tunnel_destruct(struct sock *sk)
 	list_del_rcu(&tunnel->list);
 	spin_unlock_bh(&pn->l2tp_tunnel_list_lock);
 
-	l2tp_tunnel_closeall(tunnel);
-
 	tunnel->sock = NULL;
 	l2tp_tunnel_dec_refcount(tunnel);