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

Change-Id: Ia00fcb7d98fbfce897527f67ea9690abf6fe846a
diff --git a/core/api/src/test/java/org/onosproject/mastership/MastershipServiceAdapter.java b/core/api/src/test/java/org/onosproject/mastership/MastershipServiceAdapter.java
index be1f4b9..aff67cd 100644
--- a/core/api/src/test/java/org/onosproject/mastership/MastershipServiceAdapter.java
+++ b/core/api/src/test/java/org/onosproject/mastership/MastershipServiceAdapter.java
@@ -21,6 +21,7 @@
 import org.onosproject.net.MastershipRole;
 
 import java.util.Set;
+import java.util.concurrent.CompletableFuture;
 
 /**
  * Test adapter for mastership service.
@@ -32,7 +33,7 @@
     }
 
     @Override
-    public MastershipRole requestRoleFor(DeviceId deviceId) {
+    public CompletableFuture<MastershipRole> requestRoleFor(DeviceId deviceId) {
         return null;
     }