[FIX] account: fix invoice report total incorrect

Go to Accounting / Reporting / Management / Invoices
Select Pivot view
Add "Total" measure
expand results adding "invoice #" and product

Total will be incorrect because it is summing up the value reported from
several lines of the query in which the total is taken as the invoice
total, so it will display total * # lines.

Using the price retrieved from the single lines fix the issue, but it
needs to be converted according to the currency rate of the invoice.

Moreover the test need to be modified because the amount_total variable
of the report should NOT be the move amount_total but the amount from
all the lines converted in company currency

opw-2187369

closes odoo/odoo#45050

X-original-commit: 1558bb2a
Signed-off-by: Nicolas Martinelli (nim) <nim@odoo.com>