Refactored Tests to load scenarios from file

In this changeset, I simplified the logic that is used to create
cluster data model scenarios.

Change-Id: Ia6e138d9897190d3207a70485dc62ccc34087686

watcher/tests/decision_engine/test_scheduling.py

@@ -24,8 +24,7 @@ import mock
 from watcher.decision_engine.loading import default as default_loading
 from watcher.decision_engine import scheduling
 from watcher.tests import base
-from watcher.tests.decision_engine.strategy.strategies import \
-    faker_cluster_state
+from watcher.tests.decision_engine.model import faker_cluster_state
 
 
 class TestDecisionEngineSchedulingService(base.TestCase):