test: do not force the process to exit

Using `process.exit()` in these tests is unnecessary and may mask other
problems.

Refs: https://github.com/nodejs/node/pull/29873#pullrequestreview-298851847

PR-URL: https://github.com/nodejs/node/pull/29923
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>
Reviewed-By: David Carlier <devnexen@gmail.com>
Reviewed-By: Anto Aravinth <anto.aravinth.cse@gmail.com>
Reviewed-By: Yongsheng Zhang <zyszys98@gmail.com>

test/parallel/test-https-timeout.js

@@ -51,10 +51,15 @@ const server = https.createServer(options, function() {
     console.log('got response');
   });
 
+  req.on('error', common.expectsError({
+    message: 'socket hang up',
+    code: 'ECONNRESET',
+    type: Error
+  }));
+
   req.on('timeout', common.mustCall(function() {
     console.log('timeout occurred outside');
     req.destroy();
     server.close();
-    process.exit(0);
   }));
 }));