[2.0] The command for opening a Clojure(Script) REPL window does not work

[PEZ]

Repro:

1. Jack in or connect.
2. Wait for the REPL window to open
3. Close the REPL tab
4. Issue the command Calva: Open a Clojure REPL

Expected: The REPL window should open again.

Actual: Nothing happens.

I've tracked it down to the that the clone nRepl message resulting from the command. We seem to fail to pick up the response:

https://github.com/BetterThanTomorrow/calva/blob/dev/calva/nrepl/index.ts#L145

We do succeed with this at the actual connect/jack-in, so maybe it is something wrong with the session we try to clone here.

[PEZ]

Now I think it is that we do not maintain the client.sessions object correctly.