[HttpKernel] properly handle exceptions in translator listener

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | 
| License       | MIT
| Doc PR        | 

The `setLocale()` method can throw an `\InvalidArgumentException` when
an invalid locale has been passed. These exceptions must be handled by
the `TranslatorListener` which should then pass the request's default
locale instead.
A bit of duplicated code, could be extracted.

```php
private function setLocale(Request $request)
{
    try {
        $this->translator->setLocale($request->getLocale());
    } catch (\InvalidArgumentException $e) {
        $this->translator->setLocale($request->getDefaultLocale());
    }
}
```