Azimuth can present FIPs for selection which aren't actually available

[sjpb]

Selected an IP on Arcus when creating a platform with a FIP, creation failedwith a popup:
{"parameter_values":{"cluster_floating_ip":"External IP is not available."}}

Horizon showed the FIP as Active but not mapped to a fixed IP. However the CLI showed it was mapped to a port on the ilab-60 network which was not owned by the project being used.

[sjpb]

More details/debugging: https://stackhpc.slack.com/archives/C02511MDH88/p1704967024668679