Fix bug where a cloned object would report the wrong llGetNumberOfPrims() when avatars had been sitting on the original and a different avatar sat on the copy within the same opensim session.

This was because the sitting avatars list was being cloned rather than reset.
Addresses http://opensimulator.org/mantis/view.php?id=6649
Merge branch 'master' of ssh://opensimulator.org/var/git/opensim