I'd like to reduce the number of places we have the "default"

HOw aboots

```python

from oslo.config import cfg

nvp_opts = [
    cfg.IntOpt('max_ports_per_switch',
                default=0,
                help='Maximum number of ports per lswitch'),
]
cfg.CONF.register_opts(nvp_opts, 'NVP')
```

Then where we need it its just 

```python
cfg.CONF.NVP.max_ports_per_switch
```