Support to encode and decode group id in InstructionCodec

Change-Id: Icd0947f494f572831e8b5c8d82d47c85eb074824
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 0b5e8ad..ab60909 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
@@ -50,6 +50,7 @@
     protected static final String TCP_PORT = "tcpPort";
     protected static final String UDP_PORT = "udpPort";
     protected static final String TABLE_ID = "tableId";
+    protected static final String GROUP_ID = "groupId";
     protected static final String TRIBUTARY_PORT_NUMBER = "tributaryPortNumber";
     protected static final String TRIBUTARY_SLOT_LEN = "tributarySlotLength";
     protected static final String TRIBUTARY_SLOT_BITMAP = "tributarySlotBitmap";