Add a missing field to show it in toString()

Change-Id: Ie2d4a2c37319fe60914d8e8a270f6b420e8df06e
diff --git a/core/api/src/main/java/org/onosproject/net/resource/link/LambdaResourceRequest.java b/core/api/src/main/java/org/onosproject/net/resource/link/LambdaResourceRequest.java
index acda18b..d264d5e 100644
--- a/core/api/src/main/java/org/onosproject/net/resource/link/LambdaResourceRequest.java
+++ b/core/api/src/main/java/org/onosproject/net/resource/link/LambdaResourceRequest.java
@@ -67,6 +67,7 @@
     @Override
     public String toString() {
         return MoreObjects.toStringHelper(this)
+                .add("lambda", lambda)
                 .toString();
     }
 }