Comment 2 for bug 1712008

After discussing this with Dan Smith a bit in IRC, solution #2 in comment 1 isn't great either since it would mean duplicating more of the allocation logic in multiple places, which is something we're already having to deal with between the compute service and the scheduler service right now, so we really want the scheduler to be responsible for this, so we should do something where conductor calls select_destinations with a target host and just make it do the claim, and I guess run the filters?