[FIX] product: better handle of product template copy with variants
[FIX] product: better handle of product template copy with variants

Before this commit, copying a template with variants would not copy the
attributes lines, so it didn't work as expected.

closes odoo/odoo#34128

Signed-off-by: Jérémy Kersten (jke) <56923a0c9ca793c07ff1df1013de5694062a27a6@openerp.com>
ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo