ONOS-2581 Add codec for tunnel id

Change-Id: I6ff456b0419b427945cc53fb74fd0a91cdfa758e
diff --git a/core/common/src/main/java/org/onosproject/codec/impl/InstructionCodec.java b/core/common/src/main/java/org/onosproject/codec/impl/InstructionCodec.java
index 6f680c8..6fa4ae0 100644
--- a/core/common/src/main/java/org/onosproject/codec/impl/InstructionCodec.java
+++ b/core/common/src/main/java/org/onosproject/codec/impl/InstructionCodec.java
@@ -47,6 +47,7 @@
     protected static final String SPACING_MULTIPLIER = "spacingMultiplier";
     protected static final String SLOT_GRANULARITY = "slotGranularity";
     protected static final String ETHERNET_TYPE = "ethernetType";
+    protected static final String TUNNEL_ID = "tunnelId";
 
     protected static final String MISSING_MEMBER_MESSAGE =
             " member is required in Instruction";