fix: #797
when listening on a wildcard address like "0.0.0.0" or "[::]", hysteria
actually listened on both IPv4 and IPv6. this is a well-known bug of the
golang net package.
this commit introduces a fix for that, the intended behavior will be:
0.0.0.0:443 => listen on IPv4 only
[::]:443 => listen on IPv6 only
:443 => listen on both IPv4 and IPv6
