testutils: fix simple_eth_pkt src address

A multicast source MAC address is not valid.
diff --git a/src/python/oftest/testutils.py b/src/python/oftest/testutils.py
index 33a4cc1..bf2b24a 100644
--- a/src/python/oftest/testutils.py
+++ b/src/python/oftest/testutils.py
@@ -413,8 +413,8 @@
     return pkt
 
 def simple_eth_packet(pktlen=60,
-                      eth_dst='00:01:02:03:04:05',
-                      eth_src='01:80:c2:00:00:00',
+                      eth_dst='01:80:c2:00:00:00',
+                      eth_src='00:01:02:03:04:05',
                       eth_type=0x88cc):
 
     if MINSIZE > pktlen: