change explicit_params_decorator so it uses arg1

Use one of the args explicitly in one of the decorators. This makes
sure, that the function which tries to get to the bottom of the
decorator chain, doesn't just look for the first function with named
parameters.

test_classy/view_classes.py

@@ -188,8 +188,8 @@ def decorated_function(*args, **kwargs):
 
 def explicit_params_decorator(f):
     @wraps(f)
-    def wrapper(*args, **kwargs):
-        return f(*args, **kwargs)
+    def wrapper(self, arg1, *args, **kwargs):
+        return f(self, arg1, *args, **kwargs)
     return wrapper