Bug 20126: Add simple test for ModBiblioMarc

Bug 20126: Add simple test for ModBiblioMarc

Just to confirm that we see record length and base address in a record
that has been passed through ModBiblioMarc.

Test plan:
Run the test.

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
(cherry picked from commit 1aebb1d476a1ae252758c2e89c9dbb668a60f092)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>