Use freeze_time() in other parts of our tests, too

When using `_relays_with_flags()` and similar methods it's possible
that tests start to hang without time freezing. See bug 33748 for more
details. We work around this by providing the necessary `freeze_time()`
calls meanwhile.

tests/conftest.py

@@ -3,6 +3,7 @@ import pytest
 import os.path
 from unittest import mock
 
+from freezegun import freeze_time
 from stem import descriptor
 
 from sbws import settings
@@ -120,7 +121,8 @@ def router_status(server_descriptor, router_statuses):
 @pytest.fixture(scope='function')
 def relay_list(args, conf, controller):
     """Returns a RelayList containing the Relays in the controller"""
-    return relaylist.RelayList(args, conf, controller)
+    with freeze_time("2020-02-29 10:00:00"):
+        return relaylist.RelayList(args, conf, controller)
 
 
 @pytest.fixture(scope='function')

tests/unit/lib/test_relaylist.py

@@ -71,9 +71,8 @@ def test_increment_recent_measurement_attempt(args, conf, controller):
     It also tests that the state file is updated correctly.
     """
     state = State(conf['paths']['state_fpath'])
-    # For this test it does not matter that the consensus timestamps or relays
-    # are not correct.
-    relay_list = RelayList(args, conf, controller=controller, state=state)
+    with freeze_time("2020-02-29 10:00:00"):
+        relay_list = RelayList(args, conf, controller=controller, state=state)
     # The initial count is 0 and the state does not have that key.
     assert 0 == relay_list.recent_measurement_attempt_count
     assert not state.get("recent_measurement_attempt", None)