Fail on unknown flags. Print help messsage.
Fail on unknown flags. Print help messsage.

Co-authored-by: Ralf Pannemans <40da8ab59c152564c33d37c8a792bceb07c824b1@sap.com>

smawson/istio,istio/istio,smawson/istio,smawson/istio,istio/istio,smawson/istio,smawson/istio,istio/istio,istio/istio,istio/installer,istio/istio,istio/installer,smawson/istio