session: lookup/rules table improvements and cleanup

Change-Id: I5217364220023df34d5bee071cb750df1661b093
Signed-off-by: Florin Coras <fcoras@cisco.com>
diff --git a/src/vnet/session/application.h b/src/vnet/session/application.h
index b985213..94a4e25 100644
--- a/src/vnet/session/application.h
+++ b/src/vnet/session/application.h
@@ -103,6 +103,7 @@
 } application_t;
 
 #define APP_INVALID_INDEX ((u32)~0)
+#define APP_DROP_INDEX (((u32)~0) - 1)
 #define APP_NS_INVALID_INDEX ((u32)~0)
 #define APP_INVALID_SEGMENT_MANAGER_INDEX ((u32) ~0)