// If any of the supplied actions are allowed it will be successful.
// If nil ObjectLayer is returned, the operation is not permitted.
// When nil ObjectLayer has been returned an error has always been sent to w.
func validateAdminReq(ctx context.Context, w http.ResponseWriter, r *http.Request, actions ...policy.AdminAction) (ObjectLayer, auth.Credentials) {
	// Get current object layer instance.
	objectAPI := newObjectLayerFn()