fetch_openml: allow running the test suite offline #11972
Description
When running the test suite offline, the following openml tests fails,
- test_decode_anneal
- test_decode_iris
- test_decode_anneal
- test_decode_cpu
It should be possible to run the test suite offline (all other dataset tests are skipped), and the corresponding tests should be also skipped when connection to the server can not be made.