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/caps.py b/tests/caps.py
index a3355f2..93403ea 100644
--- a/tests/caps.py
+++ b/tests/caps.py
@@ -15,7 +15,7 @@
 import oftest.parse as parse
 import basic
 
-from testutils import *
+from oftest.testutils import *
 
 #@var caps_port_map Local copy of the configuration map from OF port
 # numbers to OS interfaces