Updated openstack/openstack
Project: openstack/python-cinderclient  59177814a45b067cc47259817f8d9ff96e8d104b

Use immutable arg rather mutable arg

Passing mutable objects as default args is a known Python pitfall.
We'd better avoid this. This commit changes mutable default args with
None.

Change-Id: I7817c92069d32d1926e185ca0d0ab14e738b8b3d