[FIX] stock_account: Flaky test due to Floating point inaccuracy.

Created by: nhomar

In python it is possible that with no reason depending or some environment variables and/or different libraries the set of a floating pont as part of a dictionary give an unexpected result, in our case this test which was modified were giving incorrect floating point and Odoo already has a tool to deal with it.

Then simply we changed a forced equal in assert on unittest by the same assert but using numbers securely passed by the float_compare tool in odoo itself.

It closes #96 (closed)