Fix EZP-20988: Stale links using non-translatable attribute

Link: https://jira.ez.no/browse/EZP-20988

# Description
During the version creation process the poststore method is called several times. We need to make sure only the last record is present to avoid duplicate (and stale) elements. Since we can't update the record (no primary key in this table), we clear it and write a new one.

# Test
Manual test creating content and then checking records in database.