fix test imports

These modules were previously visible through the testutils import.
diff --git a/tests/bsn_ipmask.py b/tests/bsn_ipmask.py
index fea7caa..8304958 100644
--- a/tests/bsn_ipmask.py
+++ b/tests/bsn_ipmask.py
@@ -1,8 +1,8 @@
 """
 """
 import struct
-
 import logging
+import scapy
 
 from oftest import config
 import oftest.controller as controller