Run two-stages backups (#1)

1. Download to a local directory, archive/encrypt there
1. Push encrypted archive to remote folder

This helps when the backup destination is e.g. a NFS drive.

Also, introduce harder checks and fix some flaws.

Reviewed-on: #1
Co-authored-by: Max Mehl <mail@mehl.mx>
Co-committed-by: Max Mehl <mail@mehl.mx>

ssh-checker.sh

@@ -68,6 +68,4 @@ while read -r line; do
     echo "[SUCCESS] SSH login possible for ${RHOST}."
   fi
 
-  echo
-
 done < "$HOSTS"