Don't attempt to clear active connections unless we'ere connected

Right now with this middleware we are likely always connected, but I'm
hoping to change that soon. This is an easy change to pull out on its
own.

activerecord/lib/active_record/query_cache.rb

@@ -40,7 +40,7 @@ def self.install_executor_hooks(executor = ActiveSupport::Executor)
       executor.register_hook(self)
 
       executor.to_complete do
-        unless ActiveRecord::Base.connection.transaction_open?
+        unless ActiveRecord::Base.connected? && ActiveRecord::Base.connection.transaction_open?
           ActiveRecord::Base.clear_active_connections!
         end
       end