Setting song request rate limit to zero will permanently deny client

[kenellorando]

Setting the request rate limit to 0 will actually keep the client's IP in the rate limit database with no expiration, forever keeping it from ever making a request again after the first one is made. (at least until the database server is restarted)

0 used to be used as the number of seconds a client would be denied after they make a request, but ever since since the transition to Redis, we've been using this number as a value for "key expiration". In Redis, if this this value is set to 0, it is actually setting the key to never expire.

Expected behavior should see setting 0 to mean "no rate limiting".