Provisioner always punts on deleteService events when discovery not enabled

Reference commercial support ticket #3853.

Steps to reproduce:

1. Create a requisition with a single node, single interface, at least one service on that interface
2. Import the requisition
3. In web UI, go to Node List -> NewNode -> click on any of the services -> Delete

Expected result:
Provisioner deletes the service

Observed results:
deleteService event is created and logged, but the service is unaffected.

Suspected cause:
Provisioner.handleDeleteService method has no reachable code when discoveryEnabled is false. Matt indicated in an IM exchange that he thinks this is not the case in 1.9.