Don't assign the same external IP to two conflicting services

[Lykos153]

I can see two Services that hold the same external IP but conflict in the ports 80 and 443.

istio-system            istio-ingressgateway                                 LoadBalancer   10.104.206.154   xxx.xxx.xxx.37   15021:31197/TCP,80:31420/TCP,443:30986/TCP,31400:31746/TCP,15443:31012/TCP   491d
k8s-svc-ingress         ingress-ingress-nginx-controller                     LoadBalancer   10.110.247.169   xxx.xxx.xxx.37   80:32080/TCP,443:32443/TCP                                                   28h

The agent only has forward rules for one of them. The controller's logs say:

W0322 16:25:02.022196       1 port_mapper.go:180] relocating service "k8s-svc-ingress/ingress-ingress-nginx-controller" to a new port due to conflict on old port 8d2a5037-f3ee-4427-9f40-21d8fa2d423b
W0322 16:25:03.130451       1 port_manager.go:195] Couldn't provide floating ip for port=c49274b0-e4c5-4d1f-a0ea-036ffeaf7d79: Expected HTTP response code [201 202] when accessing [POST https://xxx:9696/v2.0/floatingips], but got 409 instead
{"NeutronError": {"type": "OverQuota", "message": "Quota exceeded for resources: ['floatingip'].", "detail": ""}}
I0322 16:25:03.130550       1 port_manager.go:173] Deleting port c49274b0-e4c5-4d1f-a0ea-036ffeaf7d79
E0322 16:25:03.937070       1 worker.go:329] error processing job SyncServiceJob("k8s-svc-ingress/ingress-ingress-nginx-controller"): No floating IP was created by OpenStack; requeueing

Expected behavior in this case:

1. Don't assign (or unassign) the external IP to (from) the newer service
2. Add an event (pending or arguably failed) to the service with a meaningful message about the exceeded quota.