Do not wait for negative check on every pkt

Rather than polling with a 1 second timeout on every negative
packet check, sleep for 1 second before doing any negative
packet checks.  Reduces PacketOutMC time by half.
diff --git a/tests/testutils.py b/tests/testutils.py
index b9e69d4..0d2dd09 100644
--- a/tests/testutils.py
+++ b/tests/testutils.py
@@ -18,6 +18,7 @@
 import oftest.parse as parse
 import logging
 import types
+import time
 
 global skipped_test_count
 skipped_test_count = 0
@@ -279,7 +280,8 @@
         assert_if.assertTrue(dataplane.match_exp_pkt(pkt, rcv_pkt),
                              "Response packet does not match send packet " +
                              "on port " + str(ofport))
-
+    if len(no_ports) > 0:
+        time.sleep(1)
     for ofport in no_ports:
         logger.debug("Negative check for pkt on port " + str(ofport))
         (rcv_port, rcv_pkt, pkt_time) = dp.poll(