Possible to configure endpoint outbound ZeroMQ channel ports to the forwarder?

Hi. I'm running into an Issue when trying to do a localhost demo of `funcX` on Binder where the `funcx-worker`s seem to be getting killed. I've opened a [topic for discussion with the Binder team on the JupyterHub Discourse here](https://discourse.jupyter.org/t/does-mybinder-limit-background-processes-differing-behavior-between-mybinder-and-repo2docker/9855) which also gives reproducible examples. In the discussion @manics has pointed to this section in the [Starting an Endpoint](https://funcx.readthedocs.io/en/latest/endpoints.html#starting-an-endpoint) docs as a potential problem

> > The endpoint establishes three outbound ZeroMQ channels to the forwarder (on the three ports returned during registration) to retrieve tasks, send results, and communicate command information.
>
> This _might_ be the problem- if those are three random ports they’ll be blocked.

To test this, is there anyway to configure those ports in the `funcX` config?

Start with the “Starting an Endpoint” documentation section and the Binder reproducible examples linked in the issue. Trace how the endpoint receives the three forwarder ports during registration and determine where configuration is handled. Done means the outbound ZeroMQ channel ports can be configured for the localhost Binder demo and the documentation explains the option.

Written by the indexing model from the issue text.