There could be big difference between ordering an instance and finding a
partition.

So in order to reflect real setup time set order's start date to moment when
partition has been found.

This reverts commit db776b07.

More then one builder can be called in same time for same invoice.

Delivery is stopped so invoice simulation WILL be present.

Let the activity system chose randomly what to do.

Scenario is used one, so just do it inline.

Side effect of returning self slave in slave list is used in SlapTool.