Correct test.

Since we're pulling config options out of the config during class
__init__ functions now, instead of during runtime,
we can't just change the homeserver config and expect runtime to
have the new value.

We need to change the vars that get set in those __init__ functions
directly. In this case, RegistrationStore.__init__.

tests/rest/client/v2_alpha/test_register.py

@@ -863,7 +863,7 @@ def make_homeserver(self, reactor, clock):
         config["account_validity"] = {"enabled": False}
 
         self.hs = self.setup_test_homeserver(config=config)
-        self.hs.config.account_validity_period = self.validity_period
+        self.hs.get_datastore()._account_validity_period = self.validity_period
 
         self.store = self.hs.get_datastore()
 
@@ -877,7 +877,7 @@ def test_background_job(self):
         """
         user_id = self.register_user("kermit_delta", "user")
 
-        self.hs.config.account_validity_startup_job_max_delta = self.max_delta
+        self.hs.get_datastore()._account_validity_startup_job_max_delta = self.max_delta
 
         now_ms = self.hs.clock.time_msec()
         self.get_success(self.store._set_expiration_date_when_missing())