Validating webook that check correct namespace for KedaController CR

[zroubalik]

Implement validating webook that check that new KedaController CustomResource is created in correct namespace (eg. keda).

https://kubernetes.io/blog/2019/03/21/a-guide-to-kubernetes-admission-controllers/

[zroubalik]

@samuelmacko ^

[zroubalik]

The work is done here: https://github.com/zroubalik/keda-olm-operator/tree/webhook

Webhook needs a valid CA Bundle included in the configuration, but CA Bundle injection for Webhooks with https://github.com/openshift/service-ca-operator works only on OpenShift >= 4.4