When testing cache issues, it is useful to log the actual key, including namespace

When using fetch or read in the ActiveSupport::Cache, ***namespaced_key(key,options)*** is used.
For these cases where you need to debug the actual cache behavior, in debug level, I think it's worth logging the actual key being used in the code, rather than the stripped down version, without the namespace.

I've added test for both Proc and string based namespaces.