Fix bug where timer would not be stopped if replica did not fetch any…

… segments.

This can happen when there is a new checkpoint published because of a SegmentInfos bump,
but the replica does not need to fetch any files.

Signed-off-by: Marc Handalian <handalm@amazon.com>

server/src/main/java/org/opensearch/indices/replication/OngoingSegmentReplications.java

@@ -115,6 +115,8 @@ void startSegmentCopy(GetSegmentFilesRequest request, ActionListener<GetSegmentF
                 }
             });
             if (request.getFilesToFetch().isEmpty()) {
+                // before completion, alert the primary of the replica's state.
+                handler.getCopyState().getShard().updateVisibleCheckpointForShard(request.getTargetAllocationId(), handler.getCopyState().getCheckpoint());
                 wrappedListener.onResponse(new GetSegmentFilesResponse(Collections.emptyList()));
             } else {
                 handler.sendFiles(request, wrappedListener);