[ADMIN_API][MGM]: Be nicer to Nova networks for deletes

Instead of deleting a bad instance instantly add to the DB with a DELETED
status so that the next run of the delete scheduler will wipe it out.

Change-Id: Ib5518ef51176729baa703eeb410911cd8437fa9c
[API] Remove deadlock detection code

It triggered for things that were not deadlocks causing more harm than good.
Also the newer algorithms in 4.x onwards should not require it.

Change-Id: I476a17ea5da5b760ab6c681a64af34b70e97c0f9