Cycles: Reduce verbosity of logging

Mainly makes logging less verbose when doing progressive sampling in viewport.

Such kind of verbosity is not really possible to be filtered out with `grep`
so let's reshuffle few lines of code.

intern/cycles/render/mesh.cpp

@@ -1232,11 +1232,11 @@ void MeshManager::device_update_displacement_images(Device *device,
 
 void MeshManager::device_update(Device *device, DeviceScene *dscene, Scene *scene, Progress& progress)
 {
-	VLOG(1) << "Total " << scene->meshes.size() << " meshes.";
-
 	if(!need_update)
 		return;
 
+	VLOG(1) << "Total " << scene->meshes.size() << " meshes.";
+
 	/* update normals */
 	foreach(Mesh *mesh, scene->meshes) {
 		foreach(uint shader, mesh->used_shaders) {