BUG: read_column did not preserve UTC tzinfo

BUG: Fixes #7777, HDFStore.read_column did not preserve timezone information
when fetching a DatetimeIndex column with tz=UTC
better to refactor the tz handling here: https://github.com/pydata/pandas/blob/master/pandas/io/pytables.py#L1467
then I think you can directly reuse it