Adding http status check option (take 2)

[bdelwood]

Adds option to open http status port and start http status server. Builds on #30

Could start working on #23

[TBBle]

Rather than mixing statusHTTP into the Service, and hence limiting functionality to those providers who've implemented the MixedProtocolLBService feature gate, what about spliting the feature up a bit?

For example, it might make sense to make the Status a separate Service, as that will also mean that in future work, it can be a ClusterIP Service and an Ingress can be added to the chart to publish the HTTP status at a different address, allowing things like https support or access control to the status page.

Another reason to rearrange this a bit is that if you only want the http port for the liveness/readiness probe then you want the ports open in the Deployment, but no Service referencing them at all. That said, the Liveness probe possibly wants to talk to the Supervisor HTTP API, rather than the server status API.

So perhaps always enable STATUS_HTTP (SERVER_PUBLIC is true by default, so the two could be tied together with a single values.yaml entry that controls both), and have the switchable thing be publishStatusHttp similar to the existing publishQueryPort.