Fix obscure "'SkipDatabaseCreation' object has no attribute '_rollback_works'" AttributeError when attempting to run django_nose tests with REUSE_DB=1 on Django trunk (pre-v1.5)

The confirm method has been removed from BaseDatabaseFeatures as cached properties (like "supports_transactions") now confirm their features automagically.
Merge branch 'patch-1' of git://github.com/dvelyk/django-nose