possibility to disable using custom hostannotation

[zetaab]

currently there is feature to define custom hostannotation https://github.com/ElisaOyj/openshift-lb-controller/blob/master/pkg/controller/controller.go#L39 However, this is not good thing if you have two separate lb-controllers in same openshift cluster. Lets say that we have two different lb-controllers, first one is taking care of external.company.com and second one internal.company.com. Now if we have this custom hostannotation defined in both, the lb-controller does not know where to expose this custom host. Currently it will expose that to both, and it is security issue if used like this.