[ptf] Consider only expected packets for timeout

"count_matched_packets" method is getting stuck in a while loop as long
as ptf server port receives any packet (Ex: in dualtor case, we do see
continuous ICMP packets on ptf port). Fix is to consider only expected
packets w.r.t timeout (similar to "count_matched_packets_all_ports" logic).

Author: vkjammala-arista

src/ptf/testutils.py

@@ -3635,14 +3635,19 @@ def count_matched_packets(test, exp_packet, port, device_number=0, timeout=None)
             "%s() requires positive timeout value." % sys._getframe().f_code.co_name
         )
 
+    last_matched_packet_time = time.time()
     total_rcv_pkt_cnt = 0
     while True:
+        if (time.time() - last_matched_packet_time) > timeout:
+            break
+
         result = dp_poll(
             test, device_number=device_number, port_number=port, timeout=timeout
         )
         if isinstance(result, test.dataplane.PollSuccess):
             if ptf.dataplane.match_exp_pkt(exp_packet, result.packet):
                 total_rcv_pkt_cnt += 1
+                last_matched_packet_time = time.time()
         else:
             break