Ticket 50439 - fix waitpid issue when pid does not exist
    
    Bug Description: In some situations, waitpid will fail with
    a no child process error, when the pid file has a value but
    no pid exists.
    
    Fix Description: Catch the exception, because in this case
    we have no pids to wait upon, so there is no harm to skip this.
    
    https://pagure.io/389-ds-base/issue/50439
    
    Author: William Brown <william@blackhats.net.au>
    
    Review by: ???