SD-1051

There were other issues which creeped in while fixing this issue.

1. After fetching an item from ingest the item appeared twice in Ingest tab, this is because `_type` is being persisted to Mongo and the same was pushed to elastic as part of `source` attribute.
2. After fetching when the document is observed in `archive` collection the `version_creator` is `None`, which doesn't make sense. Reason being when celery task starts flask.g.user is unset.
3. While inserting the document into `archive_versions` attributes like `lock_user`, `lock_session`... which are irrelevant were being inserted into the collection. Modified `metadata_schema` to have `versioned=False` for irrelevant attributes.
Initially the idea was the same but `on_update` of `ArchiveService` looks for `flask.g.user` and if not found the value of `version_creator` is set to `None`. That's the reason we are sticking `user` to `flask.g`.