[FIX] web: avoid force_reload in list editable

When creating a new record in list editable, due to previous commit 6349048, the load_record was called twice and the first record of the current list view (self.dataset.index) was used to fill the new record.
With this, we make sure a new record is indeed created.
Fix the web test to have a default_get call in mock models and increase the number of default_get assertions (for creations in list editable, the default_get is then called twice, not optimal but due to the absence of distinction between empty datarecord and filled with default values).
[FIX] account: in settings, multicurrency exchange gain/loss accounts weren't displayed because of an incorrect onchange_company_id