Replace global Conf mangling with monkeypatch

The test suite, especially for the brokers, was heavily dependant on the
success of the tests preceeding it to pass. This commit should eliminate
that dependency and allow tests to fail without affecting others.
It also removes the need to cleanup globals manually after a test.

django_q/tests/test_cached.py

@@ -10,13 +10,8 @@ from django_q.brokers import get_broker
 
 
 @pytest.fixture
-def broker():
-    Conf.DISQUE_NODES = None
-    Conf.IRON_MQ = None
-    Conf.SQS = None
-    Conf.ORM = None
-    Conf.MONGO = None
-    Conf.DJANGO_REDIS = 'default'
+def broker(monkeypatch):
+    monkeypatch.setattr(Conf, 'DJANGO_REDIS', 'default')
     return get_broker()
 
 
@@ -148,7 +143,7 @@ def test_chain(broker):
 
 
 @pytest.mark.django_db
-def test_async_class(broker):
+def test_async_class(broker, monkeypatch):
     broker.purge_queue()
     broker.cache.clear()
     a = Async('math.copysign')
@@ -186,10 +181,8 @@ def test_async_class(broker):
     assert a.result_group() == [-1]
     assert a.fetch_group() == [a.fetch()]
     # global overrides
-    Conf.SYNC = True
-    Conf.CACHED = True
+    monkeypatch.setattr(Conf, 'SYNC', True)
+    monkeypatch.setattr(Conf, 'CACHED', True)
     a = Async('math.floor', 1.5)
     a.run()
     assert a.result() == 1
-    Conf.SYNC = False
-    Conf.CACHED = False