more concise client representation in shadow.yaml

shadow/client/shadow.yaml

@@ -20,21 +20,11 @@ hosts:
       args: 100.0.0.1:6397
       start_time: 3s
 
-  client1:
-    network_node_id: 0
-    processes:
-    - path: mgen-client
-      args: "*.toml"
-      start_time: 5s
-  client2:
-    network_node_id: 0
-    processes:
-    - path: mgen-client
-      args: "*.toml"
-      start_time: 5s
-  client3:
+  client1: &client_host
     network_node_id: 0
     processes:
     - path: mgen-client
       args: "*.toml"
       start_time: 5s
+  client2: *client_host
+  client3: *client_host