Remove trailing None on calls made to the Magento's API (PHP 5.4 compatibility)

When Magento is used with PHP 5.4+, the API may return errors if we send
API calls with None in the last arguments. So, we remove all the
trailing None from the arguments before sending.

See https://bugs.launchpad.net/openerp-connector-magento/+bug/1210775
Remove trailing None in the requests recorded for the tests

Since ccfe65c removes the trailing None on the requests sent to Magento,
the data recorded for the tests must not include trailing None.
Merge pull request #28 from guewen/factorlibre-php54_compatible

Remove trailing None on calls made to the Magento's API (PHP 5.4 compatibility)