ContainerInfra: Support fixed_network/fixed_subnet/floating_ip_enabled for cluster creation

- The corresponding patch in OpenStack Magnum: https://review.opendev.org/#/c/671182/
- The three new fields were added in https://review.opendev.org/#/c/671182/6/magnum/api/controllers/v1/cluster.py

- [x] fixed_network
- [x] fixed_subnet
- [x] floating_ip_enabled