selftests: net: ksft: avoid continue when handling results

Exception handlers print the result and use continue
to skip the non-exception result printing. This makes
inserting common post-test code hard. Refactor to
avoid the continues and have only one ktap_result() call.

Reviewed-by: Petr Machata <petrm@nvidia.com>
Link: https://patch.msgid.link/20240627185502.3069139-2-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>