tap creation and setup is slow

It took almost 15 minutes to define a 676 node network with an "AMD Athlon(tm) 64 X2 Dual Core Processor 4200+":

```
./vnet -s --name grid26x26  308.47s user 490.88s system 90% cpu 14:44.42 total
```

I assume it is possible to speed this up using parallelization.
