Per experiment, cross aggregate root ssh
Regarding experiment wide ssh, we currently generate a per-aggregate root ssh key pair and optionally push that out to all nodes in an experiment, but it is a different key pair for each aggregate in the experiment.
Instead, we should derive an ssh key from the ssl private key that we generate for every portal experiment and send over to the aggregates. Then all the nodes across all aggregates in the experiment, would be able to root ssh to each other.