test: make test-http-expect-continue more strict

In test-http-expect-continue, verify that the request listener is not
called.

PR-URL: #19669
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>

test/parallel/test-http-expect-continue.js

@@ -39,7 +39,7 @@ const handler = common.mustCall((req, res) => {
   res.end(test_res_body);
 });
 
-const server = http.createServer();
+const server = http.createServer(common.mustNotCall());
 server.on('checkContinue', common.mustCall((req, res) => {
   console.error('Server got Expect: 100-continue...');
   res.writeContinue();