In case an sstable unit test case is run individually, it would fail
with exception saying that S3_... environment is not set. It's better to
skip the test-case rather than fail. If someone wants to run it from
shell, it will have to prepare S3 server (minio/AWS public bucket) and
provide proper environment for the test-case.
refs: #13569
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
Closes#13755