selftests: tc-testing: return fail if a test fails in setup/teardown

selftests: tc-testing: return fail if a test fails in setup/teardown

As of today tests throwing exceptions in setup/teardown phase are
treated as skipped but they should really be failures.

Signed-off-by: Pedro Tammela <pctammela@mojatatu.com>
Reviewed-by: Davide Caratti <dcaratti@redhat.com>
Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>
Reviewed-by: Davide Caratti <dcaratti@redhat.com>
Link: https://lore.kernel.org/r/20240124181933.75724-6-pctammela@mojatatu.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>