OrderService.saveOrder should only apply duplicate/overlap checking to DrugOrders

Per design discussion on 2015-04-29 Design Forum:

You should be allowed to have multiple active overlapping lab test orders, radiology orders, etc for the same concept, but we want to discourage this for drug orders.

Scope

TRUNK-4702 describes more significant changes to the way we do this duplicate/overlapping checking.

This ticket is only about making one specific fix that can be done much more quickly.

Acceptance Criteria

1. It is allowed to have two active TestOrders for "Complete Blood Count"
2. It is not allowed to have two active DrugOrders for "Amoxicillin 500mg tablet"

Dev Notes

This should be changed around this line.

While making this change, please move the "//Reject if there is an active order for the same orderable with overlapping schedule" comment to be next to this code (which it is supposed to refer to). It is currently in the wrong place in the code, which is confusing. Also, update the comment to be consistent with the new behavior.