Tests require a live Redis

[abkfenris]

test_api.py::test_platform_list and both test_views.py::ProxyViewTestCase tests fail without Redis, because cache_page hits the configured backend:

django_redis.exceptions.ConnectionInterrupted: Redis ConnectionError:
  Error -2 connecting to cache:6379. Name or service not known.

Confirmed by installing Redis to reach the 84-passed baseline. A LocMemCache override under DJANGO_ENV=test in settings.py makes the suite hermetic and drops a service from docker-compose.test.yaml. Cheap, and it means a failing test means a real failure.

(from #1781)