Get rid of dead code and clean up code

ml-agents/mlagents/trainers/learn.py

             docker_target_name=docker_target_name
         )
 
-    if sampler is not None:
-        sampler = load_config(sampler)
+    sampler = None
+    lesson_config = None
+    if sampler_file_path is not None:
+        sampler = load_config(sampler_file_path)
+        lesson_config = LessonController(lesson_config_path)
-    # reset_param_dict = load_config(reset_param_dict_path)
     env_factory = create_environment_factory(
         env_path,
         docker_target_name,