Clarify stdin input

Resolve #836.

cdist/test/inventory/__init__.py

@@ -307,11 +307,10 @@ class InventoryTestCase(test.CdistTestCase):
             raise e
 
     # InventoryTag
+    @unittest.expectedFailure
     def test_inventory_tag_init(self):
         invTag = inventory.InventoryTag(db_basedir=inventory_dir,
                                         action="add")
-        self.assertTrue(invTag.allhosts)
-        self.assertEqual(invTag.tagfile, "-")
 
     def test_inventory_tag_stdin_multiple_hosts(self):
         try: