Add runner logs

Author: sakthivelmanii

google-cloud-spanner/src/test/java/com/google/cloud/spanner/MockSpannerServiceImpl.java

@@ -1661,6 +1661,7 @@ public void read(final ReadRequest request, StreamObserver<ResultSet> responseOb
   public void streamingRead(
       final ReadRequest request, StreamObserver<PartialResultSet> responseObserver) {
     requests.add(request);
+    System.out.println("streamingRead");
     Preconditions.checkNotNull(request.getSession());
     Session session = getSession(request.getSession());
     if (session == null) {