The TKLBAM backup ID, the AWS S3 URI and other server/backup specific stuff are generated by the Hub and/or TKLBAM when you run 'tklbam-init'. The data related to the backup ID (and S3 URI, encryption keys, etc) is all stored in /var/lib/tklbam

Renaming (or deleting) that dir will "unlink" the server. You can then create a new backup record by (re)running 'tklbam-init'. Although note that the new backup ID won't show up in the Hub until you create a backup. The Hub generates the ID and S3 URI, but it won't actually show until there is data.