title: Files.newDirectoryStream(path) does not return files recursively
body: <p>I m expecting to see a list of all files located under path d:/test folder. However, I can only get the files directly under that folder, but not recursively. 
  Code:</p>
  
  <pre><code>        String folder = "D:/test";
          Path path = fs.getPath(folder);
          try (DirectoryStream&lt;Path&gt; directoryStream = Files.newDirectoryStream(path)) {  
              for (Path p : directoryStream) {
                  System.out.println(p.getFileName());
              }
          } catch (IOException e) {  
              e.printStackTrace();  
          }
  </code></pre>
  
  <p>result:</p>
  
  <pre><code>a.txt
  folder
  </code></pre>
  
  <p>folder structure:
  <a href="https://i.stack.imgur.com/QsXW5.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/QsXW5.png" alt="enter image description here"></a></p>