ipapython/graph.py complexity optimization
    
    Hi!
    
    I've just read the code and I saw that graph bfs uses not optimal
    for Python solution. So I've edited it with more optimal one.
    
    https://pagure.io/freeipa/issue/7051
    
    Reviewed-By: Alexander Bokovoy <abokovoy@redhat.com>
    Reviewed-By: Martin Basti <mbasti@redhat.com>