CLI/new: use configuration variable for backup directory

CLI/new: use configuration variable for backup directory

The stat is essentially replaced by the mkdir for error detection
purposes.  This changes the default location for backups to make
things tidier, even in non-split configurations. Hopefully there is
not too many user scripts relying on the previous location.

Because the default location may not exist, replace the use of stat
for error detection with a call to mkdir.