test: remove potential race condition in https renegotiation test

In test/pummel/test-https-ci-reneg-attack.js, there is a boolean that is
causing a race condition on some operating systems. It is unnecessary.
Remove it.

PR-URL: #25601
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>

test/pummel/test-https-ci-reneg-attack.js

@@ -52,15 +52,12 @@ function test(next) {
     key: fixtures.readSync('test_key.pem')
   };
 
-  let seenError = false;
-
   const server = https.createServer(options, function(req, res) {
     const conn = req.connection;
     conn.on('error', function(err) {
       console.error(`Caught exception: ${err}`);
       assert(/TLS session renegotiation attack/.test(err));
       conn.destroy();
-      seenError = true;
     });
     res.end('ok');
   });
@@ -78,7 +75,6 @@ function test(next) {
     let renegs = 0;
 
     child.stderr.on('data', function(data) {
-      if (seenError) return;
       handshakes += ((String(data)).match(/verify return:1/g) || []).length;
       if (handshakes === 2) spam();
       renegs += ((String(data)).match(/RENEGOTIATING/g) || []).length;