[services] Blob - Fix done callback logic for put reactor

Summary:
Depends on D3738

I think we should simplify the logic here. So, whenever the uploader is not initialized, we want to break the execution of doneCallback. Additionally, we keep track of whether the data already exists or not.

Test Plan: Use blob service like in D3535

Reviewers: palys-swm

Reviewed By: palys-swm

Subscribers: ashoat, palys-swm, Adrian, atul, benschac, yayabosh

Differential Revision: https://phabricator.ashoat.com/D3771