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/osl.cpp

@@ -75,11 +75,11 @@ void OSLShaderManager::reset(Scene * /*scene*/)
 
 void OSLShaderManager::device_update(Device *device, DeviceScene *dscene, Scene *scene, Progress& progress)
 {
-	VLOG(1) << "Total " << scene->shaders.size() << " shaders.";
-
 	if(!need_update)
 		return;
 
+	VLOG(1) << "Total " << scene->shaders.size() << " shaders.";
+
 	device_free(device, dscene, scene);
 
 	/* determine which shaders are in use */