fix interface allocation

there were issues with the interface code, this patch
attempts to resolve those issues:
- sets vhost to dhcp to avoid routing conflicts with the
  public interface (so that a deault gateway is set)
- manual performs ifdown/up as required
- delete the reboot code (where the assumption is that
  manually contralling interfaces should resolve the issue)
Merge pull request #15 from bodepd/interface_updates

fix interface allocation