Before this commit, the account on the original line was replaced by the
accrual account. This could be problematic for hashed journals. Instead
of having 2 different behaviors for hashed/non hashed journals, we
decided to always create 2 journal entries, which is also more academic:
* We don't replace something on an entry that has been posted
* We don't end up with taxes on the accrual account
* Accountants are used to do it this way
closesodoo/odoo#42787
Signed-off-by: Cedric Snauwaert (csn) <csn@openerp.com>