Bug 26364: Adjust unit tests

Bug 26364: Adjust unit tests

We shouldn't rely on knowing exactly which ISBNs we get, we should specifically
check for what we do or don't expect.

I believe we should return biblios that have the same isbn we passed, as it signlas we have another
biblio in the catalog that matches the one we are on.

To test:
prove -v t/db_dependent/XISBN.t

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>