[SDFAB-933] Integrate atomix-3.1.12 and expose demote API

Additionally, this patch adds unit tests for demote and
updates a bunch of testing tools

Change-Id: I9636078b08486c9167ae253f0251f72239ad2802
diff --git a/core/api/src/main/java/org/onosproject/store/primitives/DefaultLeaderElector.java b/core/api/src/main/java/org/onosproject/store/primitives/DefaultLeaderElector.java
index 6275a4f..be67325 100644
--- a/core/api/src/main/java/org/onosproject/store/primitives/DefaultLeaderElector.java
+++ b/core/api/src/main/java/org/onosproject/store/primitives/DefaultLeaderElector.java
@@ -91,6 +91,11 @@
     }
 
     @Override
+    public boolean demote(String topic, NodeId nodeId) {
+        return complete(asyncElector.demote(topic, nodeId));
+    }
+
+    @Override
     public void addStatusChangeListener(Consumer<Status> listener) {
         asyncElector.addStatusChangeListener(listener);
     }