Fix test failure when testing with Test::Harness

Fix test failure when testing with Test::Harness

Fixes an issue where, when the test suite was being run with the older
Test::Harness package, the test suite would not complete correctly due
to evaluation of $harness->runtests()->has_errors, which is only
available for the newer TAP::Parser::Aggregator code path.

Fixes #17818.

Reviewed-by: Paul Dale <pauli@openssl.org>
Reviewed-by: Richard Levitte <levitte@openssl.org>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/17823)