Bug 22437: Add test case to Merge.t

Bug 22437: Add test case to Merge.t

Test proves now that a 'destructive merge' is removed by
DelAuthority.

Test plan:
Run t/db_dependent/Authority/Merge.t. Should fail when you
do not apply the other two patches and pass with them.

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Joy Nelson <joy@bywatersolutions.com>
(cherry picked from commit c748b95d57ef625e77742785f8ced5369b326787)

Signed-off-by: Lucas Gass <lucas@bywatersolutions.com>