Avoid default mutable values in arguments
Avoid default mutable values in arguments

Mutable values shouldn't be used as default values in function
arguments [1].

[1] http://docs.python-guide.org/en/latest/writing/gotchas/

Change-Id: I3c7f915f0409c77f4c430467365eb1bcfd7757b3

openstack/python-openstackclient,dtroyer/python-openstackclient,dtroyer/python-openstackclient,openstack/python-openstackclient