[client] fix client impl selection for multiple clients

bench/client.py

@@ -73,8 +73,9 @@ def run_clients(run: int,
     err = result_dir / client_err
     csv = result_dir / client_csv
 
+    client_impl = CLIENT_IMPLEMENTATIONS[implementation]
     if not hosts:
-        cmd = CLIENT_CMD.format(exe=CLIENT_IMPLEMENTATIONS[implementation],
+        cmd = CLIENT_CMD.format(exe=client_impl,
                                 host=server_host,
                                 outfile=csv,
                                 termination_flag=termination_flag,
@@ -84,7 +85,8 @@ def run_clients(run: int,
 
     assert hosts
     assert remote_cmd
-    cmd = CLIENT_CMD.format(host=server_host,
+    cmd = CLIENT_CMD.format(exe=client_impl,
+                            host=server_host,
                             outfile='{outfile}',
                             termination_flag=termination_flag,
                             **args,