Updated openstack/openstack
Project: openstack/nova  1c2f79cfb55dc0fadc480a48212f8e52ce069b98
null
docstring fix

The docstring of class Extended_availability_zone was totally same as
Extended_server_attributes. This patch improves this docstring.

Change-Id: Ifd59d8dd149975c7f2653a0e0effadfc88d119d4