test: check server status in test-tls-psk-client

Add assertions to sequential/test-tls-psk-client to check if the
spawned OpenSSL server has exited in any way except for the expected
termination by the cleanUp() function. The added assertions will
prevent the test from spinning forever trying to connect to the
non-existent server in the case that the spawned process has exited.
Include stderr and stdout in the assertion failure message to aid
debugging.

PR-URL: #44824
Refs: #44821
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

Author: richardlau

test/sequential/test-tls-psk-client.js

@@ -23,7 +23,18 @@ const server = spawn(common.opensslCli, [
   '-psk_hint', IDENTITY,
   '-nocert',
   '-rev',
-]);
+], { encoding: 'utf8' });
+let serverErr = '';
+let serverOut = '';
+server.stderr.on('data', (data) => serverErr += data);
+server.stdout.on('data', (data) => serverOut += data);
+server.on('error', common.mustNotCall());
+server.on('exit', (code, signal) => {
+  // Server is expected to be terminated by cleanUp().
+  assert.strictEqual(code, null,
+                     `'${server.spawnfile} ${server.spawnargs.join(' ')}' unexpected exited with output:\n${serverOut}\n${serverErr}`);
+  assert.strictEqual(signal, 'SIGTERM');
+});
 
 const cleanUp = (err) => {
   clearTimeout(timeout);