Red Hat OpenShift on OpenStack installer fails with "No more IP addresses available on network"

Issue

• Installer fails with

  ERROR Error: Error creating openstack_networking_floatingip_v2: Expected HTTP response code [] when accessing [POST http://x.x.x.x:9696/v2.0/floatingips], but got 409 instead 
  ERROR {"NeutronError": {"message": "No more IP addresses available on network xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx.", "type": "IpAddressGenerationFailure", "detail": ""}}                                 
  ....
  FATAL failed to fetch Cluster: failed to generate asset "Cluster": failed to create cluster: failed to apply using Terraform