Webhook is not validating deletion of objects

[hihilla]

Shipper's validating webhook does not validate a delete action. This allows users to delete objects when there is a rollout block in the system, and Shipper will not process this properly.
For example, there is a rollout block in the system. A user deletes a release, but the parent application is not overriding this release. Shipper will not process the application since it is blocked, but all objects with owner reference pointing to the deleted release will be deleted. This causes pods to drop, without spinning new pods.