Deprecate ModMplsLabelInstruction#label()

Change-Id: I1324747adaa8ccb28077aa14b208df1083f39a3f
diff --git a/core/api/src/main/java/org/onosproject/net/flow/instructions/L2ModificationInstruction.java b/core/api/src/main/java/org/onosproject/net/flow/instructions/L2ModificationInstruction.java
index b4ec0d3..a4176b1 100644
--- a/core/api/src/main/java/org/onosproject/net/flow/instructions/L2ModificationInstruction.java
+++ b/core/api/src/main/java/org/onosproject/net/flow/instructions/L2ModificationInstruction.java
@@ -342,7 +342,13 @@
             this.mplsLabel = mplsLabel;
         }
 
-        // might want to deprecate this in the long run
+        /**
+         * @deprecated in Drake Release.
+         */
+        // Consider changing return value to MplsLabel
+        // after deprecation process so that it'll be symmetric to
+        // MplsCriterion#label()
+        @Deprecated
         public Integer label() {
             return mplsLabel.toInt();
         }