Handle os_auth_token option in keystone config
Handle os_auth_token option in keystone config

I88c2f5aa914b5fb40b6dc16a256d3e385d9aaa23 changed the option name to
auth_token for no good reason, breaking compatibility with current code.
Let's support both values.

Change-Id: I2b600b029a0e74265375dec1fe66651ab208eacd

openstack/python-zaqarclient