Ask for confirmation before killing a job

Note I answered with y, and it closed the tunnel nevertheless. Probably need to accept lower case, and ask for confirmation before closing.

Submitted cluster job 19445539
Waiting for Jupyter job to start.    
Point your browser to http://localhost:8326/
^[[Bclient_loop: send disconnect: Broken pipe

The SSH tunnel closed unexpectedly.
Would you like to reactivate the tunnel? [Y/n] y

Canceling cluster job 19445539...
Goodbye.