Fix ignore_exists signature so that unit test database can be created…

…. We can't fake these

djcelery/migrations/0001_initial.py

@@ -8,7 +8,7 @@
 from django.db.utils import DatabaseError
 
 
-def ignore_exists(self, fun, *args, **kwargs):
+def ignore_exists(fun, *args, **kwargs):
     try:
         fun(*args, **kwargs)
     except DatabaseError, exc: