Cannot delete ServiceInstance when namespace is missing

[nilebox]

Bug Report

What happened:
When namespace is missing due to #2254, Service Catalog rejects request to delete ServiceInstance. The only way to fix this is to manually re-create the namespace, then deletion works fine.

What you expected to happen:
Deletion of ServiceInstance should not rely on the existence of namespace

How to reproduce it (as minimally and precisely as possible):

1. Follow steps from Orphaned Service Catalog objects after Namespace deletion during Service Catalog API server outage #2254
2. Try deleting an "orphaned" ServiceInstance:

❯ kubectl delete serviceinstance -n ns ups-instance
Error from server (NotFound): namespaces "ns" not found

[nilebox]

I suspect that this is the issue in k8s.io/apiserver rather than Service Catalog itself.

[nilebox]

Actually, I think it's this admission controller: https://github.com/kubernetes-incubator/service-catalog/blob/2c22fc17a0cbc808f2e626f5d6c91dcd8047aa63/plugin/pkg/admission/namespace/lifecycle/admission.go, which I believe is a copy-paste of https://github.com/kubernetes/apiserver/blob/master/pkg/admission/plugin/namespace/lifecycle/admission.go

[nilebox]

The forked version of the namespace lifecycle admission controller is missing the upstream change https://github.com/kubernetes/apiserver/blob/master/pkg/admission/plugin/namespace/lifecycle/admission.go#L98-L101

We should either copy upstream changes, or get rid of our fork admission controller and replace with the upstream one.