[services] Backup - Blob Put Client - Add address constant

Summary:
Depends on D5007

Adding the blob address that's going to be used by the blob client to connect to the blob server

Test Plan: backup builds

Reviewers: jon, tomek, max, varun

Reviewed By: jon, tomek

Subscribers: ashoat, tomek, atul, abosh

Differential Revision: https://phab.comm.dev/D5008