Impacted versions: 9.0, 9.0 enterprise

Steps to reproduce:
On current runbot duplicate any posted journal entry which is balanced

Current behavior:
Error message "Cannot create unbalanced entry" is shown

Expected behavior:
New Journal entry is created in state 'draft'

Video/Screenshot link (optional):
![selection_268](https://cloud.githubusercontent.com/assets/14974044/15007437/41f45a56-11d9-11e6-84f3-b297befaa521.png)

addons/account/models/account_move.py
for move in self:
            total = 0.0
            for line in move.line_ids:
                total += line.debit
            move.amount = total
    @api.depends('line_ids.debit', 'line_ids.credit', 'line_ids.matched_debit_ids.amount', 'line_ids.matched_credit_ids.amount', 'line_ids.account_id.user_type_id.type')
    def _compute_matched_percentage(self):
        """Compute the percentage to apply for cash basis method. This value is relevant only for moves that
        involve journal items on receivable or payable accounts.
        """
        for move in self:
            total_amount = 0.0
            total_reconciled = 0.0
            for line in move.line_ids:
                if line.account_id.user_type_id.type in ('receivable', 'payable'):
                    amount = abs(line.debit - line.credit)
                    total_amount += amount
                    for partial_line in (line.matched_debit_ids + line.matched_credit_ids):
                        total_reconciled += partial_line.amount
            if total_amount == 0.0:
                move.matched_percentage = 1.0
            else:
                move.matched_percentage = total_reconciled / total_amount
    @api.one
    @api.depends('company_id')
    def _compute_currency(self):
        self.currency_id = self.company_id.currency_id or self.env.user.company_id.currency_id
    @api.multi
    def _get_default_journal(self):