prefs: Always unwrap prefs before checking Python class hierarchy

https://bugs.activestate.com/show_bug.cgi?id=101666

(integrated from komodo (trunk) change 85405 by marky)

git-svn-id: http://svn.openkomodo.com/repos/openkomodo/trunk@14383 b87d16e7-d29f-4ee1-b5ec-817d645d335f