Better handling of SSH access for collaborator sites

[ahegyes]

On sites where we are collaborators, not owners, and we lack the create_collaborator role, the command pressable:open-site-shell will fail.

It fails because it can't create the calling Team51 member as a collaborator:

For this scenario, we should just use the concierge user and try to automate the login with sshpass.

[ahegyes]

At the same time, investigate a fix for this: p1670867803746689-slack-C018UMRUN3V