fix inheritance fallout

Several places need updating to handle the new virtual classes.
diff --git a/loxi_utils/loxi_utils.py b/loxi_utils/loxi_utils.py
index 648e109..f5f9b63 100644
--- a/loxi_utils/loxi_utils.py
+++ b/loxi_utils/loxi_utils.py
@@ -417,7 +417,7 @@
 # Is class a flow modify of some sort?
 
 def cls_is_flow_mod(cls):
-    return cls in ["of_flow_modify", "of_flow_add", "of_flow_delete",
+    return cls in ["of_flow_mod", "of_flow_modify", "of_flow_add", "of_flow_delete",
                    "of_flow_modify_strict", "of_flow_delete_strict"]