tipc: Avoid reliable broadcast preparation for NACK messages

Enhance TIPC to skip unnecessary (and, in some cases, redundant)
preparation work when sending a broadcast link NACK message, since this
preparation is only required for broadcast messages that are sent in a
reliable manner. This change also fixes a bug that caused NACK messages
to be improperly counted as "TX packets" in TIPC's broadcast link
statistics.

Signed-off-by: Allan Stephens <Allan.Stephens@windriver.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>

net/tipc/bcast.c

@@ -298,6 +298,7 @@ static void bclink_send_nack(struct tipc_node *n_ptr)
 		msg = buf_msg(buf);
 		tipc_msg_init(msg, BCAST_PROTOCOL, STATE_MSG,
 			 INT_H_SIZE, n_ptr->addr);
+		msg_set_non_seq(msg, 1);
 		msg_set_mc_netid(msg, tipc_net_id);
 		msg_set_bcast_ack(msg, mod(n_ptr->bclink.last_in));
 		msg_set_bcgap_after(msg, n_ptr->bclink.gap_after);