[7.0][mrp_subproduct] subproduct quantity are not correct

Hello,

it seems there is a problem with subproduct module.

- use the head of lp:~openerp/openobject-addons/7.0
- create a new 7.0 db with demo data
- install "MRP" apps
- In Manufacturing configuration (Settings/Configuration/Manufacturing) check and apply "Produce several products from one manufacturing order"
- In Manufacturing/Bill of Materials select a Normal BoM change the quantity to 2 and add Byproducts variable with a quantity of 1
- Create a Manufacturing Order (Manufacturing/Manufacturing/Manufacturing Orders) for the updated BoM with a quantity of 1
- Confirm the production, In Finished Products we find our 2 items, the product and the 5 subproduct
- Produce the order in consume & produce mode for 1 quantity

=> The following message appears :
"Warning!

You are going to produce total 1.0 quantities of "[ADPT] USB Adapter".
But you can only produce up to total 0.5 quantities."

In addition, I think it the same as https://bugs.launchpad.net/openobject-addons/+bug/1048807

Thank for your help.

Laetitia