Centralize plugin loaders in watcher/applier

Refactor all plugin loaders in watcher/applier into
watcher/applier/loading/default.py.

Change-Id: I0f0a87d4f72ead45d34aca1b14219fd2ede42a6f
Closes-Bug: #1591095

watcher/tests/applier/actions/loading/test_default_actions_loader.py

@@ -16,7 +16,7 @@
 from __future__ import unicode_literals
 
 from watcher.applier.actions import base as abase
-from watcher.applier.actions.loading import default
+from watcher.applier.loading import default
 from watcher.tests import base
 
 

watcher/tests/applier/workflow_engine/loading/test_default_engine_loader.py

@@ -15,8 +15,8 @@
 # limitations under the License.
 from __future__ import unicode_literals
 
+from watcher.applier.loading import default
 from watcher.applier.workflow_engine import base as wbase
-from watcher.applier.workflow_engine.loading import default
 from watcher.tests import base
 
 

watcher/tests/decision_engine/strategy/strategies/test_basic_consolidation.py

@@ -19,7 +19,7 @@
 import collections
 import mock
 
-from watcher.applier.actions.loading import default
+from watcher.applier.loading import default
 from watcher.common import exception
 from watcher.decision_engine.model import model_root
 from watcher.decision_engine.strategy import strategies

watcher/tests/decision_engine/strategy/strategies/test_dummy_strategy.py

@@ -16,7 +16,7 @@
 
 import mock
 
-from watcher.applier.actions.loading import default
+from watcher.applier.loading import default
 from watcher.decision_engine.model import model_root
 from watcher.decision_engine.strategy import strategies
 from watcher.tests import base

watcher/tests/decision_engine/strategy/strategies/test_outlet_temp_control.py

@@ -19,7 +19,7 @@
 import collections
 import mock
 
-from watcher.applier.actions.loading import default
+from watcher.applier.loading import default
 from watcher.common import exception
 from watcher.decision_engine.model import model_root
 from watcher.decision_engine.model import resource

watcher/tests/decision_engine/strategy/strategies/test_workload_balance.py

@@ -19,7 +19,7 @@
 import collections
 import mock
 
-from watcher.applier.actions.loading import default
+from watcher.applier.loading import default
 from watcher.common import exception
 from watcher.decision_engine.model import model_root
 from watcher.decision_engine.model import resource