Reconcile LoadBalancer service on config-changed

[javacruft]

Ensure that the LoadBalancer service definition is updated/created on config-changed events.

This covers upgrade from previous versions of the charm which directly patched the Juju created service definition.

[gboutry]

This comment from hemanth specifically talks about upgrade hooks events:

As the service ports are not dynamic, loadbalancer need not be created/patched on upgrade-hook or update-status hook In case the service ports are modified, _reconcile_lb should run on upgrade-hook

Shouldn't we just hook the upgrade-hook and not config_changed if we're interested in upgrade charm events?

[gboutry]

This is not needed, reconcile only updates k8s SVC, not relation data, therefore it won't handle any change in the loadbalancer.