ns-3 integration; daemon core dumps upon program end

```
When running the ns-3 examples, the daemon will dump core upon end of the
program.

Segmentation fault (core dumped)

This was traced back at some point to Simulator::Destroy() not cancelling all
of the events when real-time simulator was being used; the thread executing
events then fires after the target object has been deleted.

```

Original issue reported on code.google.com by `tomh....@gmail.com` on 15 Feb 2013 at 11:38