Added flow expire/stats tests

Contributions from Google test engineers.  Basic tests for flow
expiration message generation and stats checking.  They also
added code for properly managing network prototype and wildcards
for TCP/UDP packets in parse.py.
diff --git a/src/python/oftest/parse.py b/src/python/oftest/parse.py
index c8d9ad9..13dac43 100644
--- a/src/python/oftest/parse.py
+++ b/src/python/oftest/parse.py
@@ -302,6 +302,14 @@
         match.wildcards &= ~OFPFW_NW_TOS
 
     if tcp:
+        match.nw_proto = 6
+        match.wildcards &= ~OFPFW_NW_PROTO
+    elif not tcp and udp:
+        tcp = udp
+        match.nw_proto = 17
+        match.wildcards &= ~OFPFW_NW_PROTO
+
+    if tcp:
         match.tp_src = tcp.sport
         match.wildcards &= ~OFPFW_TP_SRC
         match.tp_dst = tcp.dport