The NeutronSubnets.delete_subnets scenario assumes that the number of
users per tenant is greater or equal to the number of subnets per
Note that `number` is set to the index of the user in the `users` list.
If there are fewer users than subnets, this means that a request to
delete the subnet is submitted more than once - resulting in
This change fixes the number of users per tenant to the same value as
the number of subnets per network. Additionally, we must use round robin
user selection to ensure that the same user is not selected twice.