title: The gridfs "list" method returns empty list with non empty collection
body: <p>Can we get the count of files stored in <code>GridFS</code> using PyMongo other than using list function?</p>
  
  <p>Also, when I try the <code>list()</code> method under <code>gridfs</code>, it gives me an empty list although when there are files in the DB. Am able to retrieve the files using <code>get()</code> method by using the <code>_id</code>.
  Does the list() function return list of all the files stored under <code>gridfs</code> <code>db</code> if we save the files without filenames and depend on the <code>_id</code> value instead.</p>
  
  <p>Code:</p>
  
  <pre><code>client = pymongo.MongoClient(connect=False)
  grid_db = client['gridDB']
  fs = gridfs.GridFS(grid_db)
  # Save an image
  img_identifier = fs.put(img, encoding="utf-8")
  # List the files stored
  print fs.list()
  '''[] Console shows empty array'''
  </code></pre>