Prevent FIPs being released from project on terraform destroy

[sjpb]

Prevent users outside the openstack project "stealing" the cluster's FIPs when the cluster infra is destroyed.

This is done by removing the openstack_networking_floatingip_v2 resources and instead directly defining the addresses of FIPs to be attached to fixed IPs. This means FIPs must be manually associated to the OpenStack project, but also means they are not released from the project on terraform destroy.

Note experimenting showed the following will be required on applying these changes:

• Run terraform apply; terraform will destroy the openstack_networking_floatingip_v2. The FIP will be released from the project and the fixed to floating IP associations will be lost - but terraform will not error on this.
• Add the FIPs back into the project manually.
• Run terraform apply again. The FIPs will be reassociated with the fixed IPs.