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
if all(line.statement_id for line in self.payment_id.move_line_ids.filtered(lambda r: r.id != self.id and r.account_id.internal_type=='liquidity')):
                self.payment_id.state = 'reconciled'
        result = super(AccountMoveLine, self).write(vals)
        if self._context.get('check_move_validity', True):
            move_ids = set()
            for line in self:
                if line.move_id.id not in move_ids:
                    move_ids.add(line.move_id.id)
            self.env['account.move'].browse(list(move_ids))._post_validate()
        return result
    @api.multi
    def _update_check(self):
        """ Raise Warning to cause rollback if the move is posted, some entries are reconciled or the move is older than the lock date"""
        move_ids = set()
        for line in self:
            err_msg = _('Move name (id): %s (%s)') % (line.move_id.name, str(line.move_id.id))
            if line.move_id.state != 'draft':
                raise UserError(_('You cannot do this modification on a posted journal entry, you can just change some non legal fields. You must revert the journal entry to cancel it.\n%s.') % err_msg)
            if line.reconciled and not (line.debit == 0 and line.credit == 0):
                raise UserError(_('You cannot do this modification on a reconciled entry. You can just change some non legal fields or you must unreconcile first.\n%s.') % err_msg)
            if line.move_id.id not in move_ids:
                move_ids.add(line.move_id.id)
            self.env['account.move'].browse(list(move_ids))._check_lock_date()
        return True
    
    
    
    @api.multi
    @api.depends('ref', 'move_id')
    def name_get(self):