update worker.clj-delete "missing-tasks" checking

missing-tasks set is created by two times filter my-assignment map, so i think keys(my-assignment) contains missing-tasks set.
missing-tasks is always empty. (empty? missing-tasks) always return true. 

(let [missing-tasks (->> needed-tasks
                                       (filter (complement my-assignment)))]
                (when-not (empty? missing-tasks)
                  (log-warn "Missing assignment for following tasks: " (pr-str missing-tasks))
                  ))