message: telemetry: fix scope of subscription lock
  It looks like the lock was released too early, so before the
  _rc_status_subscription and _health_all_ok_subscription were used.
  This presumably lead to a address sanitizer failure in CI.
diff: @@ -1130,16 +1130,14 @@ void TelemetryImpl::process_sys_status(const mavlink_message_t& message)
  // If the flag is not supported yet, we fall back to the param.
  }
  - {
  std::lock_guard<std::mutex> lock(_subscription_mutex);
  if (_rc_status_subscription) {
  auto callback = _rc_status_subscription;
  auto arg = rc_status();
  _parent->call_user_callback([callback, arg]() { callback(arg); });
  }
  - }
  - const bool armable = sys_status.onboard_control_sensors_health & MAV_SYS_STATUS_PREARM_CHECK;
  + const bool armable = sys_status.onboard_control_sensors_health & MAV_SYS_STATUS_PREARM_CHECK;
  set_health_armable(armable);
  if (_health_all_ok_subscription) {
  auto callback = _health_all_ok_subscription;
  