Delete a Task Job after its grace period

[danail-branekov]

Acceptance

• Make sure that the task reporter is not running (because it is not needed for a CR setup - it talks to the CC which is not available in an Eirini-only setup and has a side effect of deleting jobs)
• Create a task via a custom resource
• Wait for the task to complete (either complete successfully, or fail)
• Make sure the K8S job stays around for at least the grace period
• Wait for the job deletion grace period
• See that the job is eventually gone
• Make sure that the K8S job is not recreated (by e.g. the tasks controller)

[kieron-dev]

As part of #198, we have introduced a check in the task-reporter which stops the reconciliation when it discovers a job is owned by a Task CR. Soon to be pushed. That helps this story a little bit, as it won't matter if the task-reporter is running or not.