Bug 17640: Fix t/db_dependent/Template/Plugin/Categories.t

Bug 17640: Fix t/db_dependent/Template/Plugin/Categories.t

These tests fail since commit 6ee8dd3a597d08ccc5122473e55790d3f21d5163
    Bug 15407: Koha::Patron::Categories - replace C4::Category->all

Indeed the patron categories plugin now returns a
Koha::Patron::Categories object and does not set a 'selected' flag.
We do not need this flag (`git grep Categories.all **/*.tt` to trust me)

Note that this patch also add a patron category to make the test passes
even if no category exist.

Test plan:
  prove t/db_dependent/Template/Plugin/Categories.t
should return green

Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>