Don't automagically run Valgrind tests. Valgrind doesn't work well in sandbox
or on all CPUs (e.g. doesn't support AVX512 still).
--- a/lib/test/test-scanner.pl
+++ b/lib/test/test-scanner.pl
@@ -48,7 +48,7 @@ my @scenarios = (
 
 plan tests => ($#scenarios + 1) * 3;
 
-chomp(my $valgrind = `which valgrind 2>/dev/null`);
+chomp(my $valgrind = `false`);
 
 if ($valgrind) {
 	$test = Test::Cmd->new(prog => "$valgrind --tool=memcheck --show-reachable=yes --leak-check=full --quiet ./test-scanner", workdir => '');