Revert "Fix strange testbots...?"

This reverts commit 74b91ca3afeddf1c9b9e6c3ff507a5e834664082.
Temporarily disabling quiz availability tests.
Issue #2368397 by esod, djdevin: Fixed non-object notice in quiz_quiz_result_load() (line 4201, 4202, 4203.
Issue #2370857 by thehong: Remove _quiz_delete_old_in_progress().