Revert "Merge pull request rails#41046 from eileencodes/dont-check-if-qc-is-enabled"

This reverts commit c97f1f1, reversing
changes made to ac7851e.

We haven't quite tracked down why yet, but this change caused our API to
not use the query cache. Our API is Sinatra mixed with Rails. We install
the Exectutor in our API so it was installed. However, (some?)
production requests were showing 0 query cache hits.

jhawthorn found that we likely need this check because if we don't the
pools returned will be a different set. He'll send a test later today.

Author: eileencodes

activerecord/lib/active_record/query_cache.rb

@@ -30,10 +30,10 @@ def self.run
 
       if ActiveRecord::Base.legacy_connection_handling
         ActiveRecord::Base.connection_handlers.each do |key, handler|
-          pools.concat(handler.connection_pool_list.each { |p| p.enable_query_cache! })
+          pools.concat(handler.connection_pool_list.reject { |p| p.query_cache_enabled }.each { |p| p.enable_query_cache! })
         end
       else
-        pools.concat(ActiveRecord::Base.connection_handler.all_connection_pools.each { |p| p.enable_query_cache! })
+        pools.concat(ActiveRecord::Base.connection_handler.all_connection_pools.reject { |p| p.query_cache_enabled }.each { |p| p.enable_query_cache! })
       end
 
       pools