Tables metadata really check the size after close

Followup to https://github.com/openmicroscopy/openmicroscopy/pull/3194
This time fetch the file-size before storage is set to None so that the DB is updated with the file-size.

One thing I'm not sure about is the effect of calling `truncate()` if a table has been opened twice, https://github.com/manics/openmicroscopy/blob/4d008c2445534a00a0d540522d066cb4b1aa130e/components/tools/OmeroPy/src/omero/tables.py#L665

FYI: I've got separate commits for fixing `setAllMetadata` https://github.com/manics/openmicroscopy/compare/manics:tables_metadata_close-12606...tables_set_all_metadata-12606?expand=1