Since 349eadc58f, test_fail() reports
the first failure. So it's safe to call test_fail() again to report a
cleanup failure when we don't want to potentially erase information
about an earlier failure.
The behavior of mbedtls_test_helper_is_psa_pristine() changes if
test_info.result was neither TEST_RESULT_SUCCESS nor
TEST_RESULT_FAILED, but this should not matter since a skipped test
should not cause mbedtls_test_helper_is_psa_pristine() to fail.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>