[product_extended_segmentation] Messages log related issues when cost doesn't get updated

Created by: osvalr

Task 4989

Required changes

It is required make a couple of changes:

• When update cost in standard_price isn't applied but segments, it's needed to write the log message on product.product instead of product.template, this happens in here as showed below:

current code:

...
tmpl_obj.message_post(cr, uid, [product_tmpl_id.id],
                                  'Not Updated Cost, But Segments only.',
                                  'I cowardly did not update Standard new \n'
                                  'price less than old price \n'
...

• Include in message log (written in product) the threshold that is based on price delta ( computed_th )