Avoid clearing redis in device rate limiter tests

Clearing all of redis masked issues with the caching logic in the
SystemLimit.for_key which isn't good. The right approach is to skip
caching when running in a test.

corehq/apps/users/device_rate_limiter.py

@@ -16,6 +16,7 @@
 
 DEVICE_LIMIT_PER_USER_KEY = "device_limit_per_user"
 DEVICE_LIMIT_PER_USER_DEFAULT = 50
+REDIS_KEY_PREFIX = "device-limiter"
 
 
 class DeviceRateLimiter:
@@ -78,7 +79,7 @@ def _get_redis_key(self, domain, user_id):
         """
         time = datetime.now(timezone.utc)
         formatted_time = time.strftime('%Y-%m-%d_%H:%M')
-        key = f"device-limiter_{domain}_{user_id}_{formatted_time}"
+        key = f"{REDIS_KEY_PREFIX}_{domain}_{user_id}_{formatted_time}"
         return key
 
     def _track_usage(self, redis_key, device_id, is_key_new=False):

corehq/apps/users/tests/test_device_rate_limiter.py

@@ -2,9 +2,8 @@
 from freezegun import freeze_time
 
 from corehq.apps.cloudcare.const import DEVICE_ID as CLOUDCARE_DEVICE_ID
-from corehq.apps.users.device_rate_limiter import DEVICE_LIMIT_PER_USER_KEY, device_rate_limiter
+from corehq.apps.users.device_rate_limiter import DEVICE_LIMIT_PER_USER_KEY, REDIS_KEY_PREFIX, device_rate_limiter
 from corehq.project_limits.models import SystemLimit
-from corehq.tests.pytest_plugins.reusedb import clear_redis
 from corehq.util.test_utils import flag_disabled, flag_enabled
 
 
@@ -15,7 +14,10 @@ class TestDeviceRateLimiter(TestCase):
 
     def setUp(self):
         SystemLimit.objects.create(key=DEVICE_LIMIT_PER_USER_KEY, limit=1)
-        self.addCleanup(clear_redis)
+
+    def tearDown(self):
+        for key in device_rate_limiter.client.scan_iter(f"{REDIS_KEY_PREFIX}*"):
+            device_rate_limiter.client.delete(key.decode('utf-8'))
 
     @flag_enabled("DEVICE_RATE_LIMITER")
     def test_allowed_if_no_devices_have_been_used_yet(self):