Change the way 1.3 flow mods are built to support rewrite actions.

Change-Id: I9c1c3059822b19d0665702162dee9904f95127d8
diff --git a/core/api/src/main/java/org/onlab/onos/net/flow/DefaultTrafficTreatment.java b/core/api/src/main/java/org/onlab/onos/net/flow/DefaultTrafficTreatment.java
index 0300079..c3fd6ed 100644
--- a/core/api/src/main/java/org/onlab/onos/net/flow/DefaultTrafficTreatment.java
+++ b/core/api/src/main/java/org/onlab/onos/net/flow/DefaultTrafficTreatment.java
@@ -201,7 +201,7 @@
         @Override
         public TrafficTreatment build() {
 
-            //If we are dropping should we just return an emptry list?
+            //If we are dropping should we just return an empty list?
             List<Instruction> instructions = new LinkedList<Instruction>();
             instructions.addAll(modifications);
             instructions.addAll(groups);