[FIX] account: Code 421 should be type Payable and not Current Liabilities

To be able to counter part the expense of the employee with the account set on his personal contact form, we need to configure the 421 account as payable.
more infos on http://www.compta-facile.com/comptabilisation-des-notes-de-frais/
The fix allows us to get that correct entry:
https://drive.google.com/a/openerp.com/file/d/0B5t9_ESHwijQemhyUjFFRzdTeVE/view?usp=sharing