container_info & account_info methods don't cache 404's

In the proxy server, the container_info and account_info methods cache 404's but they don't do anything with them.

These methods should continue to cache 404's (and 200's) but be updated to return None's immediately when they encounter the cache value of 404 without calling out the respective servers.

The "no response" and "mixed results" values (0 and -1) don't need to be cached.

Since we'll be caching non-existence care should be taken to ensure the ObjectController.PUT and AccountController.PUT methods are deleting the cached value.