fix a false positive in Inheritance proxy test

found this while investigating direct proxy implementation in firefox
(see [bug 979671](https://bugzilla.mozilla.org/show_bug.cgi?id=979671)
for more details).
fix another false positive with enumerate

again, doesn't work in firefox, but the test passes..
Merge pull request #27 from zombie/proxy-inheritance-test

fix false positives in Inheritance proxy test