winedbg: Fix 'winedbg --auto' so it does just one backtrace.

[Alexandre Julliard]

Francois Gouget <fgouget at codeweavers.com> writes:

> 'winedbg --auto' already prints a backtrace before the modules list. So 
> there is no need to print another one after everything else.

Actually there are cases where it doesn't, which is why I added
this. It's better to have two backtraces than none.

-- 
Alexandre Julliard
julliard at winehq.org