Tweak routing table checks for OpenBSD

- interfaces with shorter names (such as lo0) have whitespace appended, adjust
  the regex for this
- drop the 'default' match from the route(8) invocation.

This unbreaks a test such as:

```ruby
    should have_entry(
      :destination => '127/8',
      :interface   => 'lo0',
      :gateway     => '127.0.0.1',
    )
```