Bug 28306: Fix t/db_dependent/Koha/Objects.t

Bug 28306: Fix t/db_dependent/Koha/Objects.t

It looks like a circular dependency problem where methods are
not exported correctly

There is at least one circular dependency here:

    C4::Context -> Koha::Caches -> Koha::Cache -> C4::Context
    (-> means "uses")

The tests pass if C4::Context is loaded early, so the patch does that.

Circular dependencies should be fixed ideally, but it is a little
more complicated, and I don't have the time right now...

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