[Console] Fix `DialogHelper#ask()` with autocomplete functionality

Bug fix: yes
Feature addition: no
BC break: no
Symfony2 tests pass: yes

This PR fixes failing test after: 9d94fc7 as well as correctly resets `stty` to prevent _strange_ data showing-up in console:
![console](https://f.cloud.github.com/assets/67402/47882/673a5dae-58ed-11e2-8bab-30a7c41733f5.png)