title: S3PersistentAcceptOnceFileListFilter produces messages for the existing/synchronized files on application restart
body: <p>has anyone come across that? basically I aim to process the file once even if the application is bounced</p>
  
  <pre><code>@Bean
  public S3InboundFileSynchronizer s3InboundFileSynchronizer() throws Exception {
      S3InboundFileSynchronizer synchronizer = new S3InboundFileSynchronizer(amazonS3());
      synchronizer.setDeleteRemoteFiles(false);
      synchronizer.setPreserveTimestamp(true);
      synchronizer.setRemoteDirectory(sourceBucket + "/dir/");
      synchronizer.setFilter(new S3PersistentAcceptOnceFileListFilter(new SimpleMetadataStore(), "simpleMetadataStore"));
      return synchronizer;
  }
  
  private AmazonS3 amazonS3() throws Exception {      
      return clientFactory.getClient(AmazonS3.class);
  }
  
  @Bean
  @InboundChannelAdapter(value = "s3FilesChannel", poller = @Poller(fixedDelay = "5000"))
  public S3InboundFileSynchronizingMessageSource s3InboundFileSynchronizingMessageSource() throws Exception {
      S3InboundFileSynchronizingMessageSource messageSource =
              new S3InboundFileSynchronizingMessageSource(s3InboundFileSynchronizer());
      messageSource.setAutoCreateLocalDirectory(true);
      messageSource.setLocalDirectory(new File("c:/temp/"));
      messageSource.setLocalFilter(new FileSystemPersistentAcceptOnceFileListFilter(new SimpleMetadataStore(), "fsSimpleMetadataStore"));             
      return messageSource;
  }
  </code></pre>