message: modify update time and add log
diff: @@ -25,7 +25,7 @@ void CreateSessionProcessor::process(const cpp2::CreateSessionReq& req) {
  // The sessionId is generated by microsecond timestamp
  session.set_session_id(time::WallClock::fastNowInMicroSec());
  session.set_create_time(session.get_session_id());
  - session.set_update_time(session.get_create_time());
  + session.set_update_time(0);
  session.set_user_name(user);
  session.set_graph_addr(req.get_graph_addr());
  session.set_client_ip(req.get_client_ip());
  @@ -87,6 +87,9 @@ void UpdateSessionsProcessor::process(const cpp2::UpdateSessionsReq& req) {
  }
  if (sessionInMeta.get_update_time() > session.get_update_time()) {
  + VLOG(3) << "The session id: " << session.get_session_id()
  + << ", the new update time: " << session.get_update_time()
  + << ", the old update time: " << sessionInMeta.get_update_time();
  continue;
  }
  