[FIX] product: multi edit barcode field on template

Writing barcode on a template will only write it on the variants if the
variant count is 1. Make the field readonly on the view according to
this condition.

closes odoo/odoo#41489

X-original-commit: a67ad076f4c079f33602f01ed2b8cbf741aeffc5
Signed-off-by: Simon Lejeune (sle) <sle@openerp.com>

addons/product/views/product_template_views.xml

@@ -5,9 +5,11 @@
         <field name="model">product.template</field>
         <field name="arch" type="xml">
             <tree string="Product" multi_edit="1">
+                <field name="product_variant_count" invisible="1"/>
+
                 <field name="sequence" widget="handle" readonly="1"/>
                 <field name="default_code" optional="show"/>
-                <field name="barcode" optional="hide"/>
+                <field name="barcode" optional="hide" attrs="{'readonly': [('product_variant_count', '>', 1)]}"/>
                 <field name="name"/>
                 <field name="company_id" options="{'no_create_edit': True}"
                     groups="base.group_multi_company" optional="hide"/>