Bug 21105: Regression tests

Bug 21105: Regression tests

This patch introduces a regression test for the fixed behavior.
I also changed a oneliner regex we had for stripping query parameters
because it was causing a warning with the tests base URL
(http://localhost) because it was generating an empty baseURL.

To test:
1. Apply the regression tests patch
2. Run:
   $ kshell
  k$ prove t/db_dependent/OAI/Server.t
=> FAIL: Tests fail, the response is incorrect!
3. Apply the bug's patch
4. Repeat 2
=> SUCCESS: Tests pass! Good response!

Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>