message: admin: replace time(nullptr) with timesource's SystemTime
diff: @@ -915,17 +915,22 @@ Http::Code AdminImpl::handlerStatsRecentLookupsEnable(absl::string_view, Http::H
  Http::Code AdminImpl::handlerServerInfo(absl::string_view, Http::HeaderMap& headers,
  Buffer::Instance& response, AdminStream&) {
  - time_t current_time = time(nullptr);
  + const std::time_t current_time =
  + std::chrono::system_clock::to_time_t(server_.timeSource().systemTime());
  + const std::time_t uptime_current_epoch = current_time - server_.startTimeCurrentEpoch();
  + const std::time_t uptime_all_epochs = current_time - server_.startTimeFirstEpoch();
  +
  + ASSERT(uptime_current_epoch >= 0);
  + ASSERT(uptime_all_epochs >= 0);
  +
  envoy::admin::v3::ServerInfo server_info;
  server_info.set_version(VersionInfo::version());
  server_info.set_hot_restart_version(server_.hotRestart().version());
  server_info.set_state(
  Utility::serverState(server_.initManager().state(), server_.healthCheckFailed()));
  - server_info.mutable_uptime_current_epoch()->set_seconds(current_time -
  - server_.startTimeCurrentEpoch());
  - server_info.mutable_uptime_all_epochs()->set_seconds(current_time -
  - server_.startTimeFirstEpoch());
  + server_info.mutable_uptime_current_epoch()->set_seconds(uptime_current_epoch);
  + server_info.mutable_uptime_all_epochs()->set_seconds(uptime_all_epochs);
  envoy::admin::v3::CommandLineOptions* command_line_options =
  server_info.mutable_command_line_options();
  *command_line_options = *server_.options().toCommandLineOptions();
  