fix memory leak in attr replace when replacement fails
    
    if replacement of the attribute values fails (e.g. due to duplicate values)
    the valstoreplace is not freed - the caller expects the valueset_replace
    function to own the values passed in.  The function will now free the values
    if there was an error
    In addition, valueset_replace should not free the old values in case
    of error - it should leave the old values in the attribute
    Reviewed by: nhosoi (Thanks!)
    (cherry picked from commit 43894ffddf76baa4824c93d702ad4712e82b5b4e)