selftests/harness: Pass variant to teardown

FIXTURE_VARIANT data is passed to FIXTURE_SETUP and TEST_F as "variant".

In some cases, the variant will change the setup, such that expectations
also change on teardown. Also pass variant to FIXTURE_TEARDOWN.

The new FIXTURE_TEARDOWN logic is identical to that in FIXTURE_SETUP,
right above.

Signed-off-by: Willem de Bruijn <willemb@google.com>
Reviewed-by: Jakub Kicinski <kuba@kernel.org>
Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20201210231010.420298-1-willemdebruijn.kernel@gmail.com
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>