Use start_timer_nodelay() in protocols which rely on the retry timer

to generate the initial transmission; this cuts off around 0.3s per
instantiated connection.

src/net/tcp.c

 		goto err;
 
 	/* Start timer to initiate SYN */
-	start_timer ( &tcp->timer );
+	start_timer_nodelay ( &tcp->timer );
 
 	/* Attach parent interface, transfer reference to connection
 	 * list and return

src/net/udp/dhcp.c

 		goto err;
 
 	/* Start timer to initiate initial DHCPREQUEST */
-	start_timer ( &dhcp->timer );
+	start_timer_nodelay ( &dhcp->timer );
 
 	/* Attach parent interface, mortalise self, and return */
 	job_plug_plug ( &dhcp->job, job );

src/net/udp/tftp.c

 		goto err;
 
 	/* Start timer to initiate RRQ */
-	start_timer ( &tftp->timer );
+	start_timer_nodelay ( &tftp->timer );
 
 	/* Attach to parent interface, mortalise self, and return */
 	xfer_plug_plug ( &tftp->xfer, xfer );