Add test case for the recently solved collada instance node troubles (https://sourceforge.net/tracker/index.php?func=detail&aid=3054873&group_id=226462&atid=1067632).

git-svn-id: https://assimp.svn.sourceforge.net/svnroot/assimp/trunk@816 67173fc5-114c-0410-ac8e-9d2fd5bffc1f