Replace redis-cli copy script with redis-cli download script

[gaurav]

The script in translator-devops currently requires that Redis save the file on the server, and we then copy it over using rsync. However, there is a method for getting redis-cli to create a local RDB file from a remote Redis server: https://redis.io/docs/connect/cli/#remote-backups-of-rdb-files

I'm not sure how well this will work: rsync allows us to restart downloads, but as long as redis-cli can do the download in one go, it has some advantages in terms of not having to make sure the file has been recently saved.