[5.3] Add given guards to AuthenticationException

[hiendv]

This is the default handler for AuthenticationException in laravel/laravel

    protected function unauthenticated($request, AuthenticationException $exception)
    {
        if ($request->expectsJson()) {
            return response()->json(['error' => 'Unauthenticated.'], 401);
        }

        return redirect()->guest('login');
    }

Currently, there is no way to determine which guards are given when the exception is thrown. The PR add a setter / getter of guards to AuthenticationException.