[TCP] fix init TCP support for auto-scalled procs

When starting the TCP Main proc, be sure we initialize the MAIN<>Worker communication sockets also for the procs to be potentially scaled in the future.
`pt[n].unix_sock` is valid only for running procs (not for the "autoscale to-be"), so use the `pt[n].tcp_socks_holder[0]` holder (valid for all procs, running or not).
Thanks go to Yury Kirsanov and Slava Bendersky for reporting and helping with the troubleshooting.

net/net_tcp.c

@@ -1652,13 +1652,13 @@ static void tcp_main_server(void)
 	 * processes (get fd, new connection a.s.o)
 	 * NOTE: we add even the socks for the inactive/unfork processes - the
 	 *       socks are already created, but the triggering is from proc to
-	 *       main, having them into reactor is harmless - thye will never
+	 *       main, having them into reactor is harmless - they will never
 	 *       trigger as there is no proc on the other end to write us */
 	for (n=1; n<counted_max_processes; n++) {
 		/* skip myslef (as process) and -1 socks (disabled)
 		   (we can't have 0, we never close it!) */
-		if (n!=process_no && pt[n].unix_sock>0)
-			if (reactor_add_reader( pt[n].unix_sock, F_TCP_WORKER,
+		if (n!=process_no && pt[n].tcp_socks_holder[0]>0)
+			if (reactor_add_reader( pt[n].tcp_socks_holder[0], F_TCP_WORKER,
 			RCT_PRIO_PROC, &pt[n])<0){
 				LM_ERR("failed to add process %d (%s) unix socket "
 					"to the fd list\n", n, pt[n].desc);