Comment 6 for bug 24828

According to RFC 4472 in 5. Recommendations for DNS Resolver IPv6 Support:

"The third case is a bit more complex: optimizing away the DNS lookups
   with only link-locals is probably safe (but may be desirable with
   different lookup services that getaddrinfo() may support), as the
   link-locals are typically automatically generated when IPv6 is
   enabled, and do not indicate any form of IPv6 connectivity. That is,
   performing DNS lookups only when a non-link-local address has been
   configured on any interface could be beneficial -- this would be an
   indication that the address has been configured either from a router
   advertisement, Dynamic Host Configuration Protocol for IPv6 (DHCPv6)
   [RFC3315], or manually. Each would indicate at least some form of
   IPv6 connectivity, even though there would not be guarantees of it."