windows: fix dns lookup of localhost with ipv6

Removing a hack intended to shortcut the resolution of 'localhost'
but which doesn't work for ipv6.
This was introduced in 2876141c.
However it seems that the problems that this was trying to
circumvent has gone away ages ago, when dns resolution on
Windows started relying on Win32 GetAddrInfoW, which was
probably with be2320d4.

Fixes test-net-connect-options-ipv6.js on Windows.