Some DNS stats don't persist through restart.

I can't speak for all of these, but I've noticed over time when viewing stats through traffic_top the "DNS lookup" stat will happily persist through a restart but at the very least "DNS hits" and the "DNS Hit" percentage will not.

I'm not really sure what the scoop with "DNS Time" is...for me it's always 0.0.

Please let me know if there's any testing I can do to help out, I'd offer up a patch but C++ just isn't my cup of tea.