Fix confusing default for kube-proxy healthz bind address

[sftim]

What would you like to be amended:
https://kubernetes.io/docs/reference/command-line-tools-reference/kube-proxy/ lists:

--healthz-bind-address 0.0.0.0 Default: 0.0.0.0:10256

The IP address for the health check server to serve on (set to 0.0.0.0 for all IPv4 interfaces and :: for all IPv6 interfaces)

I'd like the default for that command line option to actually be 0.0.0.0, so that the documentation looks right. Internally, the behavior (listen on 0.0.0.0:10256 unless --healthz-bind-address sets a different bind address) should stay the same even if the implementation is updated.

Why is this needed:
This was originally reported as a website defect (and proposed fix): kubernetes/website#19213

/kind cleanup
/sig network
/sig docs
/priority backlog

[sftim]

/remove-kind feature

[athenabot]

/triage unresolved

Comment /remove-triage unresolved when the issue is assessed and confirmed.

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[jsoref]

--metrics-bind-address should be changed as well

[SataQiu]

According to

1. https://github.com/kubernetes/kubernetes/blob/master/pkg/proxy/apis/config/types.go#L117-L122

// healthzBindAddress is the IP address and port for the health check server to serve on,
// defaulting to 0.0.0.0:10256
HealthzBindAddress string
// metricsBindAddress is the IP address and port for the metrics server to serve on,
// defaulting to 127.0.0.1:10249 (set to 0.0.0.0 for all interfaces)
MetricsBindAddress string

2. https://github.com/kubernetes/kubernetes/blob/master/cmd/kube-proxy/app/server.go#L125-L135

// The fields below here are placeholders for flags that can't be directly mapped into
// config.KubeProxyConfiguration.
//
// TODO remove these fields once the deprecated flags are removed.

// master is used to override the kubeconfig's URL to the apiserver.
master string
// healthzPort is the port to be used by the healthz server.
healthzPort int32
// metricsPort is the port to be used by the metrics server.
metricsPort int32

@aojea @thockin
Maybe we should deprecate --healthz-port and --metrics-port firstly.
If this is the right direction, I am willing to send a PR for this :-)

[aojea]

🤔 it seems that those flags that allow to specify the ports were added "recently" (1.14)
#72682

I think that @thockin is the best person to define the strategy regarding configuration flags, config file, ...