Confidence feature not working on test.py for --multiple-translations

When the --multiple-translations flag is set for test.py, the following error occurs:

Traceback (most recent call last):
  File "/usr/lib/python3.10/runpy.py", line 196, in _run_module_as_main
    return _run_code(code, main_globals, None,
  File "/usr/lib/python3.10/runpy.py", line 86, in _run_code
    exec(code, run_globals)
  File "/root/.clearml/venvs-builds/3.10/task_repository/silnlp.git/silnlp/nmt/experiment.py", line 301, in <module>
    main()
  File "/root/.clearml/venvs-builds/3.10/task_repository/silnlp.git/silnlp/nmt/experiment.py", line 297, in main
    exp.run()
  File "/root/.clearml/venvs-builds/3.10/task_repository/silnlp.git/silnlp/nmt/experiment.py", line 61, in run
    self.test()
  File "/root/.clearml/venvs-builds/3.10/task_repository/silnlp.git/silnlp/nmt/experiment.py", line 85, in test
    test(
  File "/root/.clearml/venvs-builds/3.10/task_repository/silnlp.git/silnlp/nmt/test.py", line 827, in test
    results[step] = test_checkpoint(
  File "/root/.clearml/venvs-builds/3.10/task_repository/silnlp.git/silnlp/nmt/test.py", line 664, in test_checkpoint
    pair_sys, pair_refs, book_dict = load_test_data(
  File "/root/.clearml/venvs-builds/3.10/task_repository/silnlp.git/silnlp/nmt/test.py", line 507, in load_test_data
    book_dict = process_individual_books(
  File "/root/.clearml/venvs-builds/3.10/task_repository/silnlp.git/silnlp/nmt/test.py", line 402, in process_individual_books
    conf_file = stack.enter_context(conf_file_path.open("r", encoding="utf-8"))
  File "/usr/lib/python3.10/pathlib.py", line 1119, in open
    return self._accessor.open(self, mode, buffering, encoding, errors,
FileNotFoundError: [Errno 2] No such file or directory: '/root/M/MT/experiments/Demo_Matthew/test_translate_NT_1/test.trg-predictions.txt.5000.confidences.tsv'

Seems like this is due to some issue with the path name handling for the confidence file in this scenario.

Start in silnlp/nmt/test.py, tracing test_checkpoint through load_test_data to process_individual_books, where the confidence file is opened. Reproduce test.py with --multiple-translations and inspect how the confidence-file path is constructed. Done means the confidence file is found and the test completes without the reported FileNotFoundError.