Add MetadataInstruction to the API serializer namespace

Change-Id: I8edc6719a34e8699ca4364909a5092ba5158761f
(cherry picked from commit f519e3d061e21b84c61fe478969fa9dc55578810)
diff --git a/core/store/serializers/src/main/java/org/onosproject/store/serializers/KryoNamespaces.java b/core/store/serializers/src/main/java/org/onosproject/store/serializers/KryoNamespaces.java
index 2a07a61..9be102d 100644
--- a/core/store/serializers/src/main/java/org/onosproject/store/serializers/KryoNamespaces.java
+++ b/core/store/serializers/src/main/java/org/onosproject/store/serializers/KryoNamespaces.java
@@ -758,6 +758,7 @@
                     L3ModificationInstruction.ModArpEthInstruction.class,
                     L3ModificationInstruction.ModArpOpInstruction.class,
                     L3ModificationInstruction.ModArpIPInstruction.class)
+            .register(Instructions.MetadataInstruction.class)
             .build("API");
 
     /**