Rename distance_sensor.covariance to variance

src/platforms/posix/drivers/df_bebop_rangefinder_wrapper/df_bebop_rangefinder_wrapper.cpp

@@ -160,7 +160,7 @@ int DfBebopRangeFinderWrapper::_publish(struct bebop_range &data)
 
 	distance_data.orientation = distance_sensor_s::ROTATION_DOWNWARD_FACING;
 
-	distance_data.covariance = 1.0f; // TODO set correct value
+	distance_data.variance = 1.0f; // TODO set correct value
 
 	distance_data.signal_quality = -1;
 

src/platforms/posix/drivers/df_isl29501_wrapper/df_isl29501_wrapper.cpp

@@ -167,7 +167,7 @@ int DfISL29501Wrapper::_publish(struct range_sensor_data &data)
 
 	d.id = 0; // TODO set proper ID
 
-	d.covariance = 0.0f;
+	d.variance = 0.0f;
 
 	d.signal_quality = -1;
 

src/platforms/posix/drivers/df_trone_wrapper/df_trone_wrapper.cpp

@@ -173,7 +173,7 @@ int DfTROneWrapper::_publish(struct range_sensor_data &data)
 
 	d.orientation = _rotation;
 
-	d.covariance = 0.0f;
+	d.variance = 0.0f;
 
 	d.signal_quality = -1;