'Updates a subnet.
For a full list of available parameters, please refer to the official
API reference:
http://developer.openstack.org/api-ref/networking/v2/index.html#update-subnet'

def update_subnet(self, subnet_id, **kwargs):

    uri = ('/subnets/%s' % subnet_id)
    post_data = {'subnet': kwargs}
    return self.update_resource(uri, post_data)
