Loading from the bootclass path (class_loader == NULL) doesn't actually take the confusingly-named system_loader_lock_obj, because if the class loader is NULL. ie. it is parallelCapable:

// Classloaders that support parallelism, e.g. bootstrap classloader,
// do not acquire lock here
bool DoObjectLock = true;
  if (is_parallelCapable(class_loader)) {
    DoObjectLock = false;
 }

This CR is to streamline the code that doesn't take out the system_loader_lock_obj.

The only code that uses the system_loader_lock_obj is bootclasspath append code which shouldn't take out an object lock.