Complete future after Leadership withdraw is done

Change-Id: I905a78c3f80e10793506ac92783d502798ae0390
diff --git a/core/store/dist/src/main/java/org/onosproject/store/consistent/impl/DistributedLeadershipManager.java b/core/store/dist/src/main/java/org/onosproject/store/consistent/impl/DistributedLeadershipManager.java
index 439852f..91daac2 100644
--- a/core/store/dist/src/main/java/org/onosproject/store/consistent/impl/DistributedLeadershipManager.java
+++ b/core/store/dist/src/main/java/org/onosproject/store/consistent/impl/DistributedLeadershipManager.java
@@ -289,6 +289,7 @@
                                    (topic, candidates) -> candidates.stream()
                                                                     .filter(nodeId -> !localNodeId.equals(nodeId))
                                                                     .collect(Collectors.toList()));
+            future.complete(null);
         } catch (Exception e) {
             log.debug("Failed to verify (and clear) any lock this node might be holding for {}", path, e);
             retryWithdraw(path, future);