App doesn't unregister webhook on exit

[d-uzlov]

Steps to reproduce:

1. Apply basic NSM setup: https://github.com/networkservicemesh/deployments-k8s/tree/main/examples/basic
2. Make sure webhook started and self-registered: check k1 get mutatingwebhookconfigurations.admissionregistration.k8s.io
3. Delete NSM from cluster
4. Check k1 get mutatingwebhookconfigurations.admissionregistration.k8s.io again

Expected result:

List doesn't contain admission-webhook-* instance

Actual result:

Mutating webhook list still contains NSM webhook.

Additional info:

It seems like webhook tries to unregister the entry but it doesn't happen for some reason:

cmd-admission-webhook-k8s/main.go

Line 366 in cf9eb5f

_ = registerClient.Unregister(context.Background(), conf)

Also, in the deployments repo in the cleanup section we delete the webhook manually, so it must be a known behavior? But surely this must be just a half-documented bug.
https://github.com/networkservicemesh/deployments-k8s/tree/d43747cbd24515b152ef11aec6bc4f61ea2bdc88/examples/basic