message: bugfix Pksetexat Cmd will hash into wrong slot in sharding mode
  overload cmd Pksetexat current_key()
diff: @@ -669,6 +669,11 @@ class PKSetexAtCmd : public Cmd {
  public:
  PKSetexAtCmd(const std::string& name, int arity, uint16_t flag)
  : Cmd(name, arity, flag), time_stamp_(0) {}
  + virtual std::vector<std::string> current_key() const {
  + std::vector<std::string> res;
  + res.push_back(key_);
  + return res;
  + }
  virtual void Do(std::shared_ptr<Partition> partition = nullptr);
  virtual Cmd* Clone() override {
  return new PKSetexAtCmd(*this);
  