Update all Katacoda scenarios to run on Kubernetes 1.18, with
a 2 node cluster.

Fix some issues in the tasks and runs scenarios that seem to have
been undone in rebases before they were merged.

Update the Dashboard scenario to run the latest Pipeline and
Dashboard versions at time of writing.

Remove the use of the ingress in the Dashboard scenario since
it appears unstable on Katacoda with kubernetes 1.18. Using a
port-forward is sufficient for this scenario.