Prevent select parented locations in internal shipment
If the from_location in an internal movement is not just a storage, but also a parent for sub-locations, such a movement chooses randomly the exact from location.
The reason is the fact, that tryton looks for the from_location with it's childs, builds a dictionary and creates moves from that dictionary in a random sequence.
Sometimes the move is impossible, if from- and to-location are the same, sometimes the result is unexpected and sometimes it's correct.
I think we should limit the search for internal shipments to the given location without childs, because the user wants explicitly move goods from selected location to selected location.