Fixed multi-threading problem where `_local_data` attributes will only be seen by thread that imports the module.

To reproduce this bug just create basic django view that uses server side cursors and serve it using threaded runserver (default in 1.5). First hit is OK, but subsequent ones are raise `AttributeError`. As attributes of this object are local to thread, other thread will not see default values set during module import.

Side note: `global` declarations are unnecessary in this case.