[core] Enable IPv6
[core] Enable IPv6

This is the same as dee3c95 (#217), but without removing
`self.connect((host, port))`. It seems strange that we all would have
missed it, but so far re-doing this commit seems to be working in all
the ways it's supposed to.

Uname-a/knife_scraper,Uname-a/knife_scraper,Uname-a/knife_scraper