Create child orders in IgniteOrderLoaderMain created less than expected due to method is not threadsafe

[keikeicheung]

in IgniteOrderLoaderMain
It loops to create parent Orders and child order (random * 100 - 250) in multiple threads
OrdersModel.createChild it creates child order with an incremental child order id (which is not threadsafe)
hence some child orders are not "new" child order but "update" existing child order