Bug 14565: Allow koha-run-backups to backup an instance called `demo`

Bug 14565: Allow koha-run-backups to backup an instance called `demo`

We all have a `demo` instance somewhere. It is so weird that the default
script for backing up Koha has a hardcoded exclusion for instances
called like that. This patch fixes that.

To test:
1. Add a demo instance:
   $ ktd --shell
  k$ sudo koha-create --create-db demo
2. Run:
  k$ sudo debian/scripts/koha-run-backups
3. Check the backups:
  k$ ls -l /var/spool/koha/demo/
=> FAIL: No backup for the demo instance
3. Apply this patch
4. Repeat 2
=> SUCCESS: Backup made!
5. Sign off :-D

Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>