Avoid double wrap of IndexedLambda

Change-Id: I2acaa255529949e8443542904df465e6b0fbb72a
diff --git a/core/common/src/main/java/org/onosproject/codec/impl/EncodeConstraintCodecHelper.java b/core/common/src/main/java/org/onosproject/codec/impl/EncodeConstraintCodecHelper.java
index bd6ab7d..ec4ee44 100644
--- a/core/common/src/main/java/org/onosproject/codec/impl/EncodeConstraintCodecHelper.java
+++ b/core/common/src/main/java/org/onosproject/codec/impl/EncodeConstraintCodecHelper.java
@@ -142,7 +142,7 @@
                 (LambdaConstraint) constraint;
 
         return context.mapper().createObjectNode()
-                .put("lambda", lambdaConstraint.lambda().toInt());
+                .put("lambda", lambdaConstraint.lambda().index());
     }
 
     /**