LeadershipService and MastershipService/Store APIs return CompletableFutures so that callers can (optionally) chain together dependent operations

Change-Id: Ia00fcb7d98fbfce897527f67ea9690abf6fe846a
diff --git a/core/net/src/test/java/org/onosproject/net/device/impl/DeviceManagerTest.java b/core/net/src/test/java/org/onosproject/net/device/impl/DeviceManagerTest.java
index 20d55c4..d6bfda2 100644
--- a/core/net/src/test/java/org/onosproject/net/device/impl/DeviceManagerTest.java
+++ b/core/net/src/test/java/org/onosproject/net/device/impl/DeviceManagerTest.java
@@ -19,6 +19,7 @@
 import java.util.Iterator;
 import java.util.List;
 import java.util.Set;
+import java.util.concurrent.CompletableFuture;
 
 import org.junit.After;
 import org.junit.Before;
@@ -305,8 +306,8 @@
         }
 
         @Override
-        public MastershipRole requestRoleFor(DeviceId deviceId) {
-            return MastershipRole.MASTER;
+        public CompletableFuture<MastershipRole> requestRoleFor(DeviceId deviceId) {
+            return CompletableFuture.completedFuture(MastershipRole.MASTER);
         }
 
         @Override