cman: Don't crash cman_tool nodes -a
    
    cman was returning a success status but no data if the node id
    passed to cman_get_node_addrs isn't currently in the cluster.
    
    Signed-off-by: Nate Straz <nstraz@redhat.com>
    Signed-off-by: Christine Caulfield <ccaulfie@redhat.com>