Allow more flexibility when starting KSQL Server nodes

[blueedgenick]

In #774 we added the ability to specify a --queries-file argument when starting a KSQL server, which has the effect of starting the node and running all of the queries in said file.

It also disables the http listener of the server, such that no client can be connected to it. This is sometimes a desirable side-effect (gives a 'locked-down application deployment' whereby the launched queries cannot be interfered with) and sometimes it's undesirable because it removes the ability to connect interactive tooling for troubleshooting or investigative purposes.

In this feature request, i propose we update the above functionality so that supplying a --queries-file argument still runs the contents of the file but no longer has the side-effect of disabling the http listener. Instead we, as part of the same change, introduce a new, separate, command-line flag to disable the http interface if desired e.g --headless=yes or --interactive=no or similar. More complex notions of separate processing pools or similar are excluded from the above proposal. :)

[jcooklin]

This would be helpful.

[mbrancato]

I agree, I think disabling the listener should be optional and/or the server should still read and follow the ksql-server.properties configuration.

[apurvam]

I think this is a good enhancement, and simple to do .. cc @derekjn @MichaelDrogalis

[MichaelDrogalis]

Ditto #283, and +1 for fixing in the nearer term since pull queries require HTTP access to be useful.

[derekjn]

We should definitely do this, I can't think of a compelling reason why we wouldn't want to allow this.