[Cooker] install : timezone goes back to default choice when moving the mouse

[Combelles, Christophe (MED, ALTEN)]

At the end of install, when the summary is displayed, the timezone is America/NewYork (although I have done the install in french-UTF8)

- Click on the timezone to change it.
- Close the "America" branch
- move fast the mouse from left to right over "America"

The "America" branch opens by itself, and the cursor goes back to the default choice "America/NewYork"