wrap scapy with explicit imports

pylint can't handle scapy's magical imports.
diff --git a/src/python/oftest/testutils.py b/src/python/oftest/testutils.py
index e87b7a0..26c25d3 100644
--- a/src/python/oftest/testutils.py
+++ b/src/python/oftest/testutils.py
@@ -4,14 +4,7 @@
 import types
 import time
 import re
-
-try:
-    import scapy.all as scapy
-except:
-    try:
-        import scapy as scapy
-    except:
-        sys.exit("Need to install scapy for packet parsing")
+import packet as scapy
 
 import oftest
 import oftest.controller