Rogue loops that print output to stdout cause Calva to hang

[julienvincent]

I've noticed that excessive log output can cause Calva to completely hang - even after terminating the repl connection.

I was running into this while writing some bad code that caused loops to run uninterrupted. Even after terminating the repl I would still need to restart VSCode to get Calva to start responding again.

Related to #942 and #804