Skip test_list_content* on cloud implementations
requested to merge lunar/swh-objstorage:skip-testing-list-content-on-cloud-implementations into master
Running test_list_content* on cloud implementations is pretty useless
as we won’t be listing 17 billion contents from Azure or S3 in a single
thread operation. As each one takes a minute per cloud, we skip these
tests to improve the runtime of the test suite.