Pin K3s to specific version: v1.23.6

[sei-mkaar]

CI builds with k3s v1.23.7 are failing with error dialing backend: EOF during Gameboard deployment:

    virtualbox-iso.foundry-appliance: NAME: gameboard
    virtualbox-iso.foundry-appliance: LAST DEPLOYED: Mon Jun 13 11:16:56 2022
    virtualbox-iso.foundry-appliance: NAMESPACE: topomojo
    virtualbox-iso.foundry-appliance: STATUS: deployed
    virtualbox-iso.foundry-appliance: REVISION: 1
    virtualbox-iso.foundry-appliance: NOTES:
    virtualbox-iso.foundry-appliance: Course charted for gameboard.
==> virtualbox-iso.foundry-appliance: Error from server: error dialing backend: EOF

This could be related to similar issues in the K3s project:

• egress-selector cluster and pod modes break access to service endpoints using host-net pods k3s-io/k3s#5637
• Increased failure rate on exec/attach discovered on csi e2e tests k3s-io/k3s#5633

This PR pins K3s to the latest stable version, v1.23.6.

[sei-mkaar]

Actually, it looks like the error happens on this kubectl exec call to determine whether the Gameboard database is available.

foundry-appliance/foundry/topomojo/install.sh

Line 57 in 9951747

timeout 5m bash -c 'until kubectl exec postgresql-0 -n common -- env PGPASSWORD=foundry psql -lqt -U postgres | cut -d \| -f 1 | grep -qw gameboard; do sleep 5; done' || false