updated example prog to include modelnet scheduler config

doc/example/example.conf

@@ -32,6 +32,9 @@ PARAMS
    packet_size="512";
    # - type of model to use (must match with corresponding LPGROUPS entry)
    modelnet="simplenet";
+   # - message scheduling algorithm (on a per-packet basis)
+   modelnet_scheduler="fcfs"; # first come first serve
+   # modelnet_scheduler="round-robin"; # round-robin
    # - model-specific parameters
    net_startup_ns="1.5";
    net_bw_mbps="20000";