Fix IPv6 sockaddr unpacking in utils.network.host_to_ip()

Per http://docs.python.org/2/library/socket.html#socket.getaddrinfo :
> sockaddr is [...] a (address, port, flow info, scope id) **4**-tuple for AF_INET6
Merge pull request #11567 from hulu/ipv6

Fix IPv6 sockaddr unpacking in utils.network.host_to_ip()