[services] Backup - fix handling reading done in client reactors

Summary:
Depends on D3582

We should see a proper status in the terminateCallback and the error log(if an error occurs).

Test Plan:

cd services
yarn run-backup-service

Reviewers: palys-swm, varun, geekbrother, jimpo

Reviewed By: palys-swm

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

Differential Revision: https://phabricator.ashoat.com/D3583