Address ENG-10685.

Call the function from D14684 to copy logs when copying last backup UserData to the new UserKeys backup.

Depends on D14684

1. Created backup with ID=backup1, added some logs with attachments
2. Created UserKeys backup with ID=backup2

Verified (by looking into DDB) that:

• backup1's DDB contents remained untouched
• backup2 has UserData with the same blob hash but a different holders
• backup1 and backup2 both have the same logs as backup1
• All copied BlobInfos have different blob holders, also checked that these blobs have two holders in Blob service