Suggested tweaks to ec2-automate-backup-awscli

- `hostname -f` uses the hostname from /etc/hosts but this is almost always localhost. For my setup, I prefer setting the Linux hostname appropriately, which is `hostname -s` -- your preference may be different but I figured I'd suggest it.
- During disaster recovery / prevention, the original CRON job may be lost and future admins may struggle to figure out how automated backups were being created. The hostname helps with this, but also tagging with CreatedBy ec2-automate-backup will give people a term to search for, for instructions on getting things running again. Again, just a suggestion (maybe instead of this, there could just be an option to add custom tags? Or it could be added to -u ?)