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
""" Returns the data required for the invoices & payments matching of partners/accounts (list of dicts).
            If no res_ids is passed, returns data for all partners/accounts that can be reconciled.
            :param res_type: either 'partner' or 'account'
            :param res_ids: ids of the partners/accounts to reconcile, use None to fetch data indiscriminately
                of the id, use [] to prevent from fetching any data at all.
            :param account_type: if a partner is both customer and vendor, you can use 'payable' to reconcile
                the vendor-related journal entries and 'receivable' for the customer-related entries.
        """
        if res_ids != None and len(res_ids) == 0:
            
            
            return []
        res_ids = res_ids and tuple(res_ids)
        assert res_type in ('partner', 'account')
        assert account_type in ('payable', 'receivable', None)
        is_partner = res_type == 'partner'
        res_alias = is_partner and 'p' or 'a'
        query = ("""
            SELECT {0} account_id, account_name, account_code, max_date,
                   to_char(last_time_entries_checked, 'YYYY-MM-DD') AS last_time_entries_checked
            FROM (
                    SELECT {1}
                        {res_alias}.last_time_entries_checked AS last_time_entries_checked,
                        a.id AS account_id,
                        a.name AS account_name,
                        a.code AS account_code,
                        MAX(l.write_date) AS max_date