bug 1461350: Avoid runtime cache in tests
bug 1461350: Avoid runtime cache in tests

Avoid interacting with the runtime cache in tests by using the local
memory cache for django cacheback, and by changing the cache key prefix
in tests.

SphinxKnight/kuma,mozilla/kuma,a2sheppy/kuma,a2sheppy/kuma,jwhitlock/kuma,SphinxKnight/kuma,a2sheppy/kuma,Elchi3/kuma,Elchi3/kuma,Elchi3/kuma,mozilla/kuma,mozilla/kuma,a2sheppy/kuma,SphinxKnight/kuma,escattone/kuma,Elchi3/kuma,jwhitlock/kuma,a2sheppy/kuma,jwhitlock/kuma,SphinxKnight/kuma,escattone/kuma,jwhitlock/kuma,mozilla/kuma,mozilla/kuma,SphinxKnight/kuma,SphinxKnight/kuma,jwhitlock/kuma,escattone/kuma,Elchi3/kuma