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)

""" :param apply_taxes: set to False if you don't want vals['tax_ids'] to result in the creation of move lines for taxes and eventual
                adjustment of the line amount (in case of a tax included in price). This is useful for use cases where you don't want to
                apply taxes in the default fashion (eg. taxes). You can also pass 'dont_create_taxes' in context.
            :context's key `check_move_validity`: check data consistency after move line creation. Eg. set to false to disable verification that the move
                debit-credit == 0 while creating the move lines composing the move.
        """
        AccountObj = self.env['account.account']
        MoveObj = self.env['account.move']
        context = dict(self._context or {})
        amount = vals.get('debit', 0.0) - vals.get('credit', 0.0)
        if not vals.get('partner_id') and context.get('partner_id'):
            vals['partner_id'] = context.get('partner_id')
        if vals.get('move_id', False):
            move = MoveObj.browse(vals['move_id'])
            if move.date and not vals.get('date'):
                vals['date'] = move.date
        if ('account_id' in vals) and AccountObj.browse(vals['account_id']).deprecated:
            raise UserError(_('You cannot use deprecated account.'))
        if 'journal_id' in vals and vals['journal_id']:
            context['journal_id'] = vals['journal_id']
        if 'date' in vals and vals['date']:
            context['date'] = vals['date']
        if ('journal_id' not in context) and ('move_id' in vals) and vals['move_id']:
            m = MoveObj.browse(vals['move_id'])
            context['journal_id'] = m.journal_id.id
            context['date'] = m.date