Bugfix for bandwidth downling measurements.

measurement_main.py

         # prevent address already in use
         sleep(2)
         ws_filter = ""
+        congestion_control_index = 0
         if server_is_sender:
             # server sends
             if not is_tcp_probe_enabled():
             print_message("Use ws filter: {}".format(ws_filter))
             name_option = ""
             state_counter = 0
-            congestion_control_index = 0
             for n in range(1, self.config["number_of_measurements"] + 1):
                 print_message(
                     "Measurement {} of {}".format(