Fix mistake in calling super TestCase method
Fix mistake in calling super TestCase method

Oddly this caused no issue on Django <= 1.7, but it causes numerous
errors on Django 1.8.

Stupeflix/django-haystack,Stupeflix/django-haystack,vitalyvolkov/django-haystack,fisle/django-haystack,antonyr/django-haystack,streeter/django-haystack,comandrei/django-haystack,cyanut/django-haystack,comandrei/django-haystack,barseghyanartur/django-haystack,streeter/django-haystack,django-searchstack/django-searchstack,ruimashita/django-haystack,comandrei/django-haystack,kuanyui/django-haystack,streeter/django-haystack,ruimashita/django-haystack,elishowk/django-haystack,jannon/django-haystack,barseghyanartur/django-haystack,jannon/django-haystack,barseghyanartur/django-haystack,antonyr/django-haystack,fisle/django-haystack,sgaist/django-haystack,fisle/django-haystack,sgaist/django-haystack,jannon/django-haystack,eventials/django-haystack,antonyr/django-haystack,cyanut/django-haystack,elishowk/django-haystack,eventials/django-haystack,kuanyui/django-haystack,django-searchstack/django-searchstack,Stupeflix/django-haystack,vitalyvolkov/django-haystack,vitalyvolkov/django-haystack,sgaist/django-haystack,kuanyui/django-haystack,elishowk/django-haystack,ruimashita/django-haystack,django-searchstack/django-searchstack,eventials/django-haystack,cyanut/django-haystack,celerityweb/django-haystack,celerityweb/django-haystack,celerityweb/django-haystack