[ONOS-4258] Initial implementation of supporting extension in REST

- Support Nicira extension

Change-Id: I62bf4417e43459727ce7d4b1ac929c6cf0b7826f
diff --git a/core/api/src/main/java/org/onosproject/net/flow/instructions/ExtensionTreatmentType.java b/core/api/src/main/java/org/onosproject/net/flow/instructions/ExtensionTreatmentType.java
index cf2400c..df9789e 100644
--- a/core/api/src/main/java/org/onosproject/net/flow/instructions/ExtensionTreatmentType.java
+++ b/core/api/src/main/java/org/onosproject/net/flow/instructions/ExtensionTreatmentType.java
@@ -79,6 +79,15 @@
         this.type = type;
     }
 
+    /**
+     * Returns extension treatment type.
+     *
+     * @return extension treatment type
+     */
+    public int type() {
+        return type;
+    }
+
     @Override
     public int hashCode() {
         return Objects.hash(type);