daemon: fix IPv6 address corruption in lookup_hostname()

daemon: fix IPv6 address corruption in lookup_hostname()

getaddrinfo() is called with AF_UNSPEC hints, so it may return IPv6
results. However, the code unconditionally casts ai_addr to
sockaddr_in and passes AF_INET to inet_ntop(). On IPv6-only hosts,
this reads from the wrong struct offset, producing garbage IP
addresses.

Fix this by checking ai_family and extracting the address pointer
into a local variable before calling inet_ntop() once with the
correct family. Die on unexpected address families.

Signed-off-by: Sebastien Tardif <sebtardif@ncf.ca>
Signed-off-by: Junio C Hamano <gitster@pobox.com>