Centralize plugin loaders in decision engine

Refactor planner loader in watcher/decision_engine/planner/loading/default.py
to watcher/decision_engine/loading/default.py.

Change-Id: I3d4f3668d2269b5a77a35f4470a4d1c96c3128dd
Closes-Bug: #1591092

watcher/decision_engine/planner/loading/default.py

@@ -1,26 +0,0 @@
-# -*- encoding: utf-8 -*-
-# Copyright (c) 2015 b<>com
-#
-# Licensed under the Apache License, Version 2.0 (the "License");
-# you may not use this file except in compliance with the License.
-# You may obtain a copy of the License at
-#
-# http://www.apache.org/licenses/LICENSE-2.0
-#
-# Unless required by applicable law or agreed to in writing, software
-# distributed under the License is distributed on an "AS IS" BASIS,
-# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
-# implied.
-# See the License for the specific language governing permissions and
-# limitations under the License.
-#
-
-from __future__ import unicode_literals
-
-from watcher.common.loader import default
-
-
-class DefaultPlannerLoader(default.DefaultLoader):
-    def __init__(self):
-        super(DefaultPlannerLoader, self).__init__(
-            namespace='watcher_planners')

watcher/decision_engine/planner/manager.py

@@ -18,7 +18,7 @@
 from oslo_config import cfg
 from oslo_log import log
 
-from watcher.decision_engine.planner.loading import default as loader
+from watcher.decision_engine.loading import default as loader
 
 
 LOG = log.getLogger(__name__)