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

[wendymiaoo]

Hi @keikeicheung , Wendy would like to take a look into this if it hasn't been picked by others yet.

[wendymiaoo]

Hi @junaidzm13, @keikeicheung , could you help review the code?

[wendymiaoo]

Added @naleeha for review as well :)