move testutils to src/python/oftest

testutils.py needs to be in a common location for different directories of
tests to use it.
diff --git a/tests/openflow_protocol_messages.py b/tests/openflow_protocol_messages.py
index 8f2593f..c8ad1b8 100644
--- a/tests/openflow_protocol_messages.py
+++ b/tests/openflow_protocol_messages.py
@@ -18,7 +18,7 @@
 import oftest.parse as parse
 import basic
 
-from testutils import *
+from oftest.testutils import *
 from time import sleep
 from FuncUtils import *