[services] Backup - Send log - initialize put reactor method

Summary:
Depends on D3586

Adding a method called initializePutReactor for initializing the put client reactor

Test Plan:

cd services
yarn run-backup-service

Reviewers: palys-swm, geekbrother

Reviewed By: palys-swm

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

Differential Revision: https://phabricator.ashoat.com/D3646