driver: added list_files function

storagedriver.py

 from disk import Disk
 from storagecelery import celery
-from os import path, unlink, statvfs
+from os import path, unlink, statvfs, listdir, mkdir
+from shutil import move
 from celery.contrib.abortable import AbortableTask
+import logging
+
+logger = logging.getLogger(__name__)
+
+trash_directory = "trash"
 
 
 @celery.task()
@@ -10,6 +16,12 @@ def list(dir):
 
 
 @celery.task()
+def list_files(datastore):
+    return [l for l in listdir(datastore) if
+            path.isfile(path.join(datastore, l))]
+
+
+@celery.task()
 def create(disk_desc):
     disk = Disk.deserialize(disk_desc)
     disk.create()