Fix progress indicator when discarding a snapshot

[Sander]

On my computer (Vista SP2) it takes about 20 minutes to discard a snapshot (of a not-running virtual machine). However the time indicator starts at about 5 seconds, and raises slowly until it reaches ~5-6 minutes. In this time 5 minutes have past already.

Is it plausible to

1. Speed the discarding up
2. Correct the 'time-left'-timer

[Frank Mehnert]

I doubt that speeding up the discard snapshot operation is possible. Note that discarding means that two disk images needs to be merged which can be very time consuming depending of the number of changes which were made after the snapshot was created. Well, the progress indicator should show more sane values of course.

[umoeller]

This should have been fixed with version 3.1 to the extent that it's fixable. Unfortunately merging diff images ("discarding" in the old terminology) is not a linear process because the progress depends on which sectors are occupied in the diff images and thus need to be copied, which is not easily predictable.