[BUG]: self_contained_coordinator r.ping() is using 6379 port and not redis_proc_start_port

[filipecosta90]

  File "/usr/local/lib/python3.6/dist-packages/redis_benchmarks_specification/__self_contained_coordinator__/self_contained_coordinator.py", line 506, in process_self_contained_coordinator_stream
    r.ping()
  File "/usr/local/lib/python3.6/dist-packages/redis/commands/core.py", line 1053, in ping
    return self.execute_command("PING", **kwargs)
  File "/usr/local/lib/python3.6/dist-packages/redis/client.py", line 1215, in execute_command
    conn = self.connection or pool.get_connection(command_name, **options)
  File "/usr/local/lib/python3.6/dist-packages/redis/connection.py", line 1386, in get_connection
    connection.connect()
  File "/usr/local/lib/python3.6/dist-packages/redis/connection.py", line 620, in connect
    raise ConnectionError(self._error_message(e))
redis.exceptions.ConnectionError: Error 111 connecting to localhost:6379. Connection refused.