We used to set query_cache_type to 0 in the default settings but we were
also setting query_cache_size to a non-zero/non-default value, which was
in turn re-enabling the query cache. Update the configuration to reflect
the actual cache state and make sure query_cache_size is set to zero for
the "query_cache_type = 0" case.

Now that the setting controls the real state of the query cache, disable
it for bbs.archlinux.org; its hit rate is small compared to insert rate.