Upgrade Atomix to 2.0.8 and simplify consistent primitive operation/event IDs

Change-Id: I33b68a134a7f3d016a8947bffc3cea0b90bd4bd2
diff --git a/core/store/primitives/src/main/java/org/onosproject/store/primitives/resources/impl/AtomixDocumentTreeEvents.java b/core/store/primitives/src/main/java/org/onosproject/store/primitives/resources/impl/AtomixDocumentTreeEvents.java
index 43f2a20..47dcd31 100644
--- a/core/store/primitives/src/main/java/org/onosproject/store/primitives/resources/impl/AtomixDocumentTreeEvents.java
+++ b/core/store/primitives/src/main/java/org/onosproject/store/primitives/resources/impl/AtomixDocumentTreeEvents.java
@@ -24,17 +24,11 @@
  * Atomix document tree events.
  */
 public enum AtomixDocumentTreeEvents implements EventType {
-    CHANGE("change");
-
-    private final String id;
-
-    AtomixDocumentTreeEvents(String id) {
-        this.id = id;
-    }
+    CHANGE;
 
     @Override
     public String id() {
-        return id;
+        return name();
     }
 
     public static final KryoNamespace NAMESPACE = KryoNamespace.newBuilder()