The proxy healthz server assumed that kube-proxy would regularly call
UpdateTimestamp() even when nothing changed, but that's no longer
true. Fix it to only report unhealthiness when updates have been
received from the apiserver but not promptly pushed out to
iptables/ipvs.
Kube-proxy runs two different health servers; one for monitoring the
health of kube-proxy itself, and one for monitoring the health of
specific services. Rename them to "ProxierHealthServer" and
"ServiceHealthServer" to make this clearer, and do a bit of API
cleanup too.
The existing healthcheck lib was pretty complicated and was hiding some
bugs (like the count always being 1), This is a reboot of the interface
and implementation to be significantly simpler and better tested.