Method set_connection

src/msg/Message.h:371–377

    return connection;
  }
  void set_connection(ConnectionRef c) {
#ifdef WITH_CRIMSON
    // In crimson, conn is independently maintained outside Message.
    ceph_assert(c == nullptr);
#endif
    connection = std::move(c);
  }
  CompletionHook* get_completion_hook() { return completion_hook; }
  void set_completion_hook(CompletionHook *hook) { completion_hook = hook; }
  void set_byte_throttler(ThrottleInterface *t) {