[UlyssesSPDataLoaderAdapter] fix iterator reset (#7472)
Fixes https://github.com/snowflakedb/ArcticTraining/issues/254 - to
support multi-epoch training with `UlyssesSPDataLoaderAdapter`.
Thanks to @yanrui27 for the fix
Signed-off-by: Stas Bekman <stas@stason.org>
Co-authored-by: Rui Yan <49115835+yanrui27@users.noreply.github.com>
