[IMP] Make sure invoice_state of picking is used when creating extra moves and take price of related move if there is one

When we would copy, it gives problems as it won't be invoiced the correct way on sale, so we provide for a simpler solution.
Merge pull request #2918 from odoo-dev/8.0-wmsextramoves-jco

[IMP] Make sure invoice_state of picking is used when creating extra moves