hagl: fix flow for terrain starting

unit tests are passing

src/modules/ekf2/EKF/control.cpp

@@ -437,6 +437,8 @@ void Ekf::controlOpticalFlowFusion()
 		_inhibit_flow_use = ((preflight_motion_not_ok || flight_condition_not_ok) && !is_flow_required)
 				    || !_control_status.flags.tilt_align;
 
+		controlHaglFlowFusion();
+
 		// Handle cases where we are using optical flow but we should not use it anymore
 		if (_control_status.flags.opt_flow) {
 			if (!(_params.fusion_mode & MASK_USE_OF)

src/modules/ekf2/EKF/terrain_estimator.cpp

@@ -57,7 +57,6 @@ void Ekf::controlHaglFusion()
 	}
 
 	controlHaglRngFusion();
-	controlHaglFlowFusion();
 	controlHaglFakeFusion();
 
 	// constrain terrain position to be a minimum of _params.rng_gnd_clearance larger than _state.pos(2)
@@ -188,10 +187,7 @@ void Ekf::controlHaglFlowFusion()
 
 	if (_flow_data_ready) {
 		const bool continuing_conditions_passing = _control_status.flags.in_air
-		                                           && !_control_status.flags.opt_flow
-							   && _control_status.flags.gps
-							   && isTimedOut(_time_last_hagl_fuse, 5e6f); // TODO: check for range_finder hagl aiding instead?
-							   /* && !_hagl_sensor_status.flags.range_finder; */
+							   && _control_status.flags.gps;
 		const bool starting_conditions_passing = continuing_conditions_passing;
 
 		if (_hagl_sensor_status.flags.flow) {

src/modules/ekf2/test/test_EKF_terrain_estimator.cpp

@@ -112,7 +112,7 @@ TEST_F(EkfTerrainTest, setFlowAndRangeTerrainFusion)
 
 	// THEN: By default, both rng and flow aiding are active
 	EXPECT_TRUE(_ekf_wrapper.isIntendingTerrainRngFusion());
-	EXPECT_FALSE(_ekf_wrapper.isIntendingTerrainFlowFusion());
+	EXPECT_TRUE(_ekf_wrapper.isIntendingTerrainFlowFusion());
 	const float estimated_distance_to_ground = _ekf->getTerrainVertPos();
 	EXPECT_NEAR(estimated_distance_to_ground, simulated_distance_to_ground, 1e-3f);