fix(grafana): delete dangling ingress

[weisdd]

• grafana:
  • there's an old well-known issue in the grafana controller where it does not attempt to delete an Ingress when someone nullifies the ingress spec in the Grafana CR (.spec.ingress = {} -> .spec.ingress = nil), the PR intends to fix that:
    • as, at the moment, we allow users to pick only a single ingress resource type, I've put the clean up logic outside of the reconcileIngress function;
    • if we agree on the implementation, we can add similar logic for other ingress resource types.

[Baarsgaard]

LGTM
I assume we have a similar issue for OpenShift routes then?

[weisdd]

@Baarsgaard yeah, we do :)

[weisdd]

I'll open a separate PR for dangling Routes soon. With #2300 merged, we can easily test the behaviour.