Fix input parameter processing for client num nodes (#653)

src/bin/client-demo.rs

@@ -211,7 +211,7 @@ fn main() {
         threads = t.to_string().parse().expect("integer");
     }
 
-    if let Some(n) = matches.value_of("nodes") {
+    if let Some(n) = matches.value_of("num_nodes") {
         num_nodes = n.to_string().parse().expect("integer");
     }