Refactor to not copy from original method

Instead we can call the original method if the cluster is RBAC. The
original method already checks if helm is available, and that it is not
not_installable

app/models/clusters/applications/knative.rb

@@ -17,11 +17,11 @@ module Clusters
       include ::Clusters::Concerns::ApplicationData
       include AfterCommitQueue
 
+      alias_method :original_set_initial_status, :set_initial_status
       def set_initial_status
-        return unless not_installable?
-        return unless verify_cluster?
+        return unless cluster&.platform_kubernetes_rbac?
 
-        self.status = status_states[:installable]
+        original_set_initial_status
       end
 
       state_machine :status do
@@ -131,10 +131,6 @@ module Clusters
 
         [Gitlab::Kubernetes::KubectlCmd.delete("--ignore-not-found", "-f", METRICS_CONFIG)]
       end
-
-      def verify_cluster?
-        cluster&.application_helm_available? && cluster&.platform_kubernetes_rbac?
-      end
     end
   end
 end