FIX: ensure we have no dangling db connections on threads

This correct 10 second timeouts in dev mode, when reloader kicks in

lib/scheduler/defer.rb

@@ -74,6 +74,8 @@ module Scheduler
       end
     rescue => ex
       Discourse.handle_job_exception(ex, message: "Processing deferred code queue")
+    ensure
+      ActiveRecord::Base.connection_handler.clear_active_connections!
     end
   end