Enforce sizelimit in permission-find, post_callback returns truncated
    
    We actually perform two searches in permission-find. The first looks
    for matches within the permission object itself. The second looks at
    matches in the underlying aci.
    
    We need to break out in two places. The first is if we find enough
    matches in the permission itself. The second when we are appending
    matches from acis.
    
    The post_callback() definition needed to be modified to return
    the truncated value so a plugin author can modify that value.
    
    https://fedorahosted.org/freeipa/ticket/2322