message: Call quit from default exit handler and for kill
diff: @@ -60,14 +60,12 @@ result<message> drop(scheduled_actor*, message_view&) {
  // -- static helper functions --------------------------------------------------
  void scheduled_actor::default_error_handler(scheduled_actor* ptr, error& x) {
  - ptr->fail_state_ = std::move(x);
  - ptr->setf(is_terminated_flag);
  + ptr->quit(std::move(x));
  }
  void scheduled_actor::default_down_handler(scheduled_actor* ptr, down_msg& x) {
  aout(ptr) << "*** unhandled down message [id: " << ptr->id()
  - << ", name: " << ptr->name() << "]: " << to_string(x)
  - << std::endl;
  + << ", name: " << ptr->name() << "]: " << to_string(x) << std::endl;
  }
  void scheduled_actor::default_exit_handler(scheduled_actor* ptr, exit_msg& x) {
  @@ -542,8 +540,7 @@ scheduled_actor::categorize(mailbox_element& x) {
  unlink_from(em.source);
  // exit_reason::kill is always fatal
  if (em.reason == exit_reason::kill) {
  - fail_state_ = std::move(em.reason);
  - setf(is_terminated_flag);
  + quit(std::move(em.reason));
  } else {
  call_handler(exit_handler_, this, em);
  }
  