Increase default max-shared-lb from 2

[wouterh-dev]

/kind feature

What happened:

It is possible to share a LoadBalancer between multiple Kubernetes services: https://github.com/kubernetes/cloud-provider-openstack/blob/master/docs/openstack-cloud-controller-manager/expose-applications-using-loadbalancer-type-service.md#sharing-load-balancer-with-multiple-services

But the default setting of max-shared-lb is only 2, so you can only have 2 Kubernetes services that share a LoadBalancer. This makes it useful, but very limited.

If there is a good reason for the default to be this low it would be great for it to be documented.

What you expected to happen:

To be able to create more than 2 services that share a LoadBalancer without having to convince my Kubernetes provider to change the setting from the default

How to reproduce it:

1. Create a Service with Kind=LoadBalancer
2. Create a second Service that shares the loadbalancer.openstack.org/load-balancer-address & loadbalancer.openstack.org/load-balancer-id annotations but uses different ports.
3. Observe this succeeds
4. Create a third Service that shares the loadbalancer.openstack.org/load-balancer-address & loadbalancer.openstack.org/load-balancer-id annotations but uses different ports.
5. Observe this gives the error message: load balancer NAME already shared with 2 Services