Merge "Use atomic variable to avoid race condition"

  std::map<uint16_t, std::unique_ptr<iso_cis>> conn_hdl_to_cis_map_;

  std::map<uint16_t, std::unique_ptr<iso_bis>> conn_hdl_to_bis_map_;

  uint16_t iso_credits_;

  std::atomic_uint16_t iso_credits_;

  uint16_t iso_buffer_size_;

  uint32_t last_big_create_req_sdu_itv_;