Add option to start new VDI session

[aidanheerdegen]

Sometimes users have issues starting a jupyter notebook from an existing VDI session. The script times out, perhaps due to the node running very slowly.

It is possible to increase the timeouts in the script, but it is usually sufficient to terminate the session and a new session will be started, hopefully on a different VDI node.

It is possible to use the /opt/vdi/bin/session-ctl command directly to list the available sessions to get the pid of the session and use

ssh vdi.nci.org.au /opt/vdi/bin/session-ctl terminate --jobid $ID

to terminate it, but it would be simpler to add a flag to the script to do this for users.