advpack: Skip some tests if not in interactive mode because they pop up dialogs.

[Saulius Krasuckas]

* On Tue, 13 Nov 2007, Francois Gouget wrote:
> 
> This was causing the advpack:install test to time out on my Win98, WinXP 
> and Win2003 VMs.

Would it be nice to create some closer-thread for closing poped up dialogs 
in places of code known for that behaviour?  (Probably, for non 
interactive mode only)