Fixes a bug in the PortForwarder in which it would not respect the port to listen on.

[LukeButters]

Background

instead it always used the ephemeral one.

When constructing the port forwarder this last paramater:

public PortForwarder(Uri originServer,
            TimeSpan sendDelay,
            Func<BiDirectionalDataTransferObserver> biDirectionalDataTransferObserverFactory,
            int numberOfBytesToDelaySending,
            ILogger logger,
            int? listeningPort = null)

Was not at all used, and instead we always listened on port 0 aka start listening on a free port, even in the case the user set listeningPort to a value.

With this change if you call that ctor with listeningPort = 123 it WILL now listen on port 123.

This is an issue when using the port forwarder ad hoc e.g. in a command line program.

How to review this PR

Quality ✔️

Pre-requisites

• I have read How we use GitHub Issues for help deciding when and where it's appropriate to make an issue.
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• I have considered appropriate testing for my change.

[david-staniec-octopus]

LGTM