message: mission: fail if mission item is unsupported
  These two breaks were missing. If an item is unsupported we have to
  exit the parsing and return the result instead of continuing.
diff: @@ -674,6 +674,7 @@ std::pair<Mission::Result, Mission::MissionPlan> MissionImpl::convert_to_result_
  } else {
  LogErr() << "Mission item DO_CHANGE_SPEED params unsupported";
  result_pair.first = Mission::Result::Unsupported;
  + break;
  }
  } else if (int_item.command == MAV_CMD_NAV_LOITER_TIME) {
  @@ -692,6 +693,7 @@ std::pair<Mission::Result, Mission::MissionPlan> MissionImpl::convert_to_result_
  // is not trivial
  LogErr() << "Mission item NAV_DELAY params unsupported";
  result_pair.first = Mission::Result::Unsupported;
  + break;
  }
  } else if (int_item.command == MAV_CMD_NAV_RETURN_TO_LAUNCH) {
  