invoice_view.xml

<?xml version="1.0" encoding="utf-8"?>
<openerp>
    <data>

        <record id="invoice_supplier_form" model="ir.ui.view">
            <field name="name">account.invoice.supplier.form2</field>
            <field name="model">account.invoice</field>
            <field name="inherit_id" ref="account.invoice_supplier_form" />
            <field name="arch" type="xml">
                <xpath expr="//field[@name='invoice_line']/tree[@string='Invoice lines']/field[@name='product_id']" position="before">
                    <field name="sequence" widget="handle"/>
                </xpath>
            </field>
        </record>

        <record id="invoice_form" model="ir.ui.view">
            <field name="name">account.invoice.form</field>
            <field name="model">account.invoice</field>
            <field name="inherit_id" ref="account.invoice_form" />
            <field name="priority">2</field>
            <field name="arch" type="xml">
                <xpath expr="//field[@name='invoice_line']/tree[@string='Invoice Lines']/field[@name='product_id']" position="before">
                    <field name="sequence" widget="handle"/>
                </xpath>
            </field>
        </record>

    </data>
</openerp>