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

test/run_tests.pl

@@ -314,10 +314,12 @@ my $harness = $package->new(\%tapargs);
 my $ret =
     $harness->runtests(map { [ abs2rel($_, rel2abs(curdir())), basename($_) ] }
                        @preps);
-die if $ret->has_errors;
-$ret =
+
+if (ref($ret) ne "TAP::Parser::Aggregator" || !$ret->has_errors) {
+    $ret =
         $harness->runtests(map { [ abs2rel($_, rel2abs(curdir())), basename($_) ] }
                            sort { reorder($a) cmp reorder($b) } keys %tests);
+}
 
 # If this is a TAP::Parser::Aggregator, $ret->has_errors is the count of
 # tests that failed.  We don't bother with that exact number, just exit