Try to use ModMplsHeaderInstruction and ModVlanHeaderInstruction

Change-Id: I0b486907ef718a6dfa3e92696397fe5a7e851aed
diff --git a/core/common/src/main/java/org/onosproject/codec/impl/EncodeInstructionCodecHelper.java b/core/common/src/main/java/org/onosproject/codec/impl/EncodeInstructionCodecHelper.java
index 3d1ed2f..d04acf5 100644
--- a/core/common/src/main/java/org/onosproject/codec/impl/EncodeInstructionCodecHelper.java
+++ b/core/common/src/main/java/org/onosproject/codec/impl/EncodeInstructionCodecHelper.java
@@ -142,9 +142,8 @@
                 result.put(InstructionCodec.MPLS_LABEL, modMplsLabelInstruction.label().toInt());
                 break;
             case MPLS_PUSH:
-                final L2ModificationInstruction.PushHeaderInstructions pushHeaderInstructions =
-                        (L2ModificationInstruction.PushHeaderInstructions) l2Instruction;
-
+                final L2ModificationInstruction.ModMplsHeaderInstruction pushHeaderInstructions =
+                        (L2ModificationInstruction.ModMplsHeaderInstruction) l2Instruction;
                 result.put(InstructionCodec.ETHERNET_TYPE,
                         pushHeaderInstructions.ethernetType().toShort());
                 break;