The log_statsd_host value can now be an IPv6 address or a hostname
which only resolves to an IPv6 address. In both cases, the new
behavior is to use an AF_INET6 socket on which .sendto() is called
with the originally-configured hostname (or IP). This means the
Swift process is not caching a DNS resolution for the lifetime of
the process (a good thing).
If a hostname resolves to both an IPv6 or IPv4 address, an AF_INET
socket is used (i.e. only the IPv4 address will receive the UDP
packet).
The old behavior is preserved: any invalid IP address literals and
failures in DNS resolution or actual StatsD packet sending do not
halt the process or bubble up; they are caught, logged, and
otherwise ignored.
Change-Id: Ibddddcf140e2e69b08edf3feed3e9a5fa17307cf