broker: add to client list only after completion of reconnect dance

[irriden]

Close #97

@Evanfeenstra no rush - when you can let me know what you think of the overall approach here.

Most noteworthy - when sending to a specific client - I remove the check on its presence in the client list.

Is this even an issue worth addressing ? Still open to other ways of thinking about this.

[irriden]

And d4aa398 potentially closes #96.

Should we instead only fail after x number of retries ?

Key is to return at some point if we never get a response :)

[Evanfeenstra]

seems like a fine approach, but i wonder if there is a simpler way to achieve the same result (simply not wait forever if the message is not from CLN directly)

dance_complete_rx.recv().expect is probably not ideal, it will kill the reconnect thread if that expect is ever called. You can check if let Ok() instead maybe