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
invoice = self._context.get('invoice', False)
        self._post_validate()
        for move in self:
            move.line_ids.create_analytic_lines()
            if move.name == '/':
                new_name = False
                journal = move.journal_id
                if invoice and invoice.move_name and invoice.move_name != '/':
                    new_name = invoice.move_name
                else:
                    if journal.sequence_id:
                        
                        sequence = journal.sequence_id
                        if invoice and invoice.type in ['out_refund', 'in_refund'] and journal.refund_sequence:
                            sequence = journal.refund_sequence_id
                        new_name = sequence.with_context(ir_sequence_date=move.date).next_by_id()
                    else:
                        raise UserError(_('Please define a sequence on the journal.'))
                if new_name:
                    move.name = new_name
        return self.write({'state': 'posted'})
    @api.multi
    def button_cancel(self):