test: allow inspector to reopen with same port

Test checks that if you open the inspector with '0' (pick a random free
port), close it, then reopen it, you get a different port. However this
isn't necessarily true.

PR-URL: https://github.com/nodejs/node/pull/14320
Fixes: https://github.com/nodejs/node/issues/14316
Refs: https://github.com/nodejs/node/issues/14316#issuecomment-315680755
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

test/parallel/test-inspector-open.js

@@ -68,7 +68,6 @@ function tryToCloseWhenClosed(msg) {
 function reopenAfterClose(msg) {
   assert.strictEqual(msg.cmd, 'url');
   const port = url.parse(msg.url).port;
-  assert.notStrictEqual(port, firstPort);
   ping(port, (err) => {
     assert.ifError(err);
     process.exit();