Container breakpoints occasionally marked invalid (but still hit)

Using `vscode-remote-try-node` container:

Set breakpoint in the handler for:
```js
const app = express();
app.get('/', (req, res) => {
	console.log("hello");
	res.send('Hello remote world!\n');
});
```

It will (sometimes) get shown as unbound. However, upon navigating to the page it will still be hit. I was not able to repro outside of a container.