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
company_ids = set()
        all_accounts = []
        partners = set()
        for line in self:
            company_ids.add(line.company_id.id)
            all_accounts.append(line.account_id)
            if (line.account_id.internal_type in ('receivable', 'payable')):
                partners.add(line.partner_id.id)
            if line.reconciled:
                raise UserError(_('You are trying to reconcile some entries that are already reconciled!'))
        if len(company_ids) > 1:
            raise UserError(_('To reconcile the entries company should be the same for all entries!'))
        if len(set(all_accounts)) > 1:
            raise UserError(_('Entries are not of the same account!'))
        if not all_accounts[0].reconcile:
            raise UserError(_('The account %s (%s) is not marked as reconciliable !') % (all_accounts[0].name, all_accounts[0].code))
        if len(partners) > 1:
            raise UserError(_('The partner has to be the same on all lines for receivable and payable accounts!'))
        
        remaining_moves = self.auto_reconcile_lines()
        
        if writeoff_acc_id and writeoff_journal_id and remaining_moves:
            all_aml_share_same_currency = all([x.currency_id == self[0].currency_id for x in self])