message: Add mission clear to integration tests.
diff: @@ -249,7 +249,23 @@ void test_mission(
  // Wait until we're done.
  std::this_thread::sleep_for(std::chrono::seconds(1));
  }
  - LogInfo() << "Disarmed, exiting.";
  + LogInfo() << "Disarmed.";
  +
  + {
  + LogInfo() << "Clearing mission.";
  + auto prom = std::make_shared<std::promise<void>>();
  + auto future_result = prom->get_future();
  + mission->clear_mission_async([prom](Mission::Result result) {
  + ASSERT_EQ(result, Mission::Result::SUCCESS);
  + prom->set_value();
  + LogInfo() << "Cleared mission, exiting.";
  + });
  +
  + auto status = future_result.wait_for(std::chrono::seconds(2));
  + ASSERT_EQ(status, std::future_status::ready);
  + future_result.get();
  + }
  +
  }
  std::shared_ptr<MissionItem> add_mission_item(
  