[backup] Revoke holders of replaced log items

Summary:
ENG-7005 : Handle blob holders of replaced logs
It's possible that backup logs will be replaced if there is an upload request send with the same log id (and we need to allow it as a part of the transactional log upload). This diff fixes an issue where we wouldn't clear the holders of the replaced logs.

Test Plan: Modify the backup integration test to only send logs with id of 1. Made sure that at the end there were only two blobs with holders -> one for the compaction and one for the last log sent.

Reviewers: kamil, marcin

Reviewed By: kamil

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D11355