BF: @with_rw_directory must return decorated call

As it was - many tests were simply not accounted/run at all

Author: yarikoptic

Diff for: git/test/lib/helper.py

@@ -111,6 +111,8 @@ def wrapper(self):
             if not keep:
                 rmtree(path)
 
+    return wrapper
+
 
 def with_rw_repo(working_tree_ref, bare=False):
     """