Option to disable de-duplication while adding binaries in the DataStore

Sometimes, running upload/downloads in parallel can create race conditions with the backend e.g. Azure blob store complains about access condition as the etag changes.

In the DataStore whenever an add for a blob already available is called the lastModified time is updated. And option to disable de-duplication will mostly write a new blob with a new id which will not lead to this race condition but will impact performance.