django-banish stops working after cache TIMEOUT reached

[groovecoder]

Steps to reproduce:

1. Set the default cache timeout to 60s using CACHES argument.
2. Throw a bunch of abusive traffic at django. (e.g., ab -c 2 -n 1000 http://127.0.0.1:8000/)

Expected results:
After the traffic trips the ABUSE_THRESHOLD, django-banish should respond with 403 for the client

Actual results:
After the traffic trips the ABUSE_THRESHOLD, django-banish responds with 403 for the client until the CACHES TIMEOUT value is reached. Then django-banish forgets that the IP is banished. It allows the requests thru until the same client trips the ABUSE_THRESHOLD again. And repeats this pattern.