some small fixes for #1001 (#1012)


diff --git a/modules/core/src/main/java/org/apache/fluo/core/impl/TransactionImpl.java b/modules/core/src/main/java/org/apache/fluo/core/impl/TransactionImpl.java
index ef13bc8..f4ebacf 100644
--- a/modules/core/src/main/java/org/apache/fluo/core/impl/TransactionImpl.java
+++ b/modules/core/src/main/java/org/apache/fluo/core/impl/TransactionImpl.java
@@ -1140,11 +1140,13 @@
   }
 
   class CommittedTestStep extends CommitStep {
+    @Override
     CompletableFuture<Boolean> getMainOp(CommitData cd) {
       cd.commitObserver.committed();
       return CompletableFuture.completedFuture(true);
     }
 
+    @Override
     CompletableFuture<Void> getFailureOp(CommitData cd) {
       throw new IllegalStateException("Failure not expected");
     }