Bug 41012: (bug 40622 follow-up) Clear the MSS cache

For some reasons t/db_dependent/ILSDI_Services.t fails if run after
t/db_dependent/api/v1/biblios.t

When we modify the MARC subfield structure from the tests we must flush
the cache.

Actually I don't understand why the tests are even passing.

I have not tracked down why it only fails when run after t/db_dependent/api/v1/biblios.t

Test plan:
0. Do not apply this patch
1. prove t/db_dependent/api/v1/biblios.t t/db_dependent/ILSDI_Services.t
It fails
    #   Failed test 'Title hidden in output as expected'
    #   at t/db_dependent/ILSDI_Services.t line 874.
    #          got: '1'
    #     expected: '0'
2. Apply this patch, repeat 1.
=> it's green!

Signed-off-by: David Cook <dcook@prosentient.com.au>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Lucas Gass <lucas@bywatersolutions.com>
(cherry picked from commit b6aab57065)
Signed-off-by: Paul Derscheid <paul.derscheid@lmscloud.de>

t/db_dependent/ILSDI_Services.t

@@ -836,6 +836,7 @@ subtest 'GetRecords' => sub {
         { frameworkcode => $biblio->frameworkcode, tagfield => "245", tagsubfield => "a" } );
     $framework_f245a->hidden('8');
     $framework_f245a->store();
+    Koha::Caches->get_instance()->flush_all;
 
     my $patron = $builder->build(
         {