When creating a service of type 'LoadBalancer', you create
a cloud network load balancer.
This provides an externally-accessible IP address that sends
traffic to the correct port on your cluster nodes.
The external IP address is stored in k8s service's status
information (under loadbalancer/ingress/ip).
Kuryr implements this capability using OpenStack floating IP
functionality.
This patch updates Kuryr to store external IP information only after
LB was entirely configured in OpenStack.
Change-Id: I1d43f03d49d6e760c859f219aa9a4c209087c753
Closes-Bug: 1756730