[lotest] Use network device receive queue freezing

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/usr/lotest.c

 	ifstat ( sender );
 	ifstat ( receiver );
 
+	/* Freeze receive queue processing on the receiver, so that we
+	 * can extract all received packets.
+	 */
+	netdev_rx_freeze ( receiver );
+
 	/* Perform loopback test */
 	for ( successes = 0 ; ; successes++ ) {
 
 				goto done;
 			}
 			/* Poll network devices */
-			netdev_poll ( sender );
-			netdev_poll ( receiver );
+			net_poll();
 		} while ( ( iobuf = netdev_rx_dequeue ( receiver ) ) == NULL );
 
 		/* Check received packet */
  done:
 	printf ( "\n");
 	free_iob ( iobuf );
+	netdev_rx_unfreeze ( receiver );
 
 	/* Dump final statistics */
 	ifstat ( sender );