Fixes #5793: Add the rudder-agent utilities to rudder-agent

Ticket: http://www.rudder-project.org/redmine/issues/5793

To be merged in 3.0
This will fail because the initial-promises dir doesn't exist. But beyond that, it's a unrelated change. Please remove it from this PR and make a separate ticket for it.

If something breaks because of this change, we'll never think to look back here.