Bug 16172: fix OAI Server tests broken by bug 15946

 Bug 16172: fix OAI Server tests broken by bug 15946

This patch makes t/db_dependent/OAI/Server.t test for the correct
schema and metadata namespace.

To test:
- Run
  $ prove t/db_dependent/OAI/Server.t
=> FAIL: Tests fail due to differences in the output.
- Apply the patch
- Run
  $ prove t/db_dependent/OAI/Server.t
=> SUCCESS: Tests now pass
- Sign off

Regards

Signed-off-by: Mark Tompsett <mtompset@hotmail.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Brendan A Gallagher <brendan@bywatersolutions.com>