Changing the Unified Limits limit value to 0 does not work

There is an issue when setting the Unified Limits resource_limit value to 0.

The problem is caused by the following condition:

if parsed_args.resource_limit:
    kwargs["resource_limit"] = parsed_args.resource_limit

Since 0 evaluates to False, the value is skipped and is not passed to update_limit(). The condition should check for None instead.

https://github.com/openstack/python-openstackclient/blob/master/openstackclient/identity/v3/limit.py