Fixed tense consistency (used past) in statuses

In several places in Watcher, there are statuses which corresponds
to a status in the respective life cycle. There were used past tense
everywhere, except "SUCCESS" which was written in present tense.

So I searched for all the occurences of this state, and replaced them
with their past tense form.

Change-Id: Ic41def96d1a608da06a1e394e24704d4f06ab32a
Closes-Bug: #1520276

watcher/tests/objects/test_action_plan.py

@@ -97,13 +97,13 @@ class TestActionPlanObject(base.DbTestCase):
                                    autospec=True) as mock_update_action_plan:
                 action_plan = objects.ActionPlan.get_by_uuid(
                     self.context, uuid)
-                action_plan.state = 'SUCCESS'
+                action_plan.state = 'SUCCEEDED'
                 action_plan.save()
 
                 mock_get_action_plan.assert_called_once_with(
                     self.context, uuid)
                 mock_update_action_plan.assert_called_once_with(
-                    uuid, {'state': 'SUCCESS'})
+                    uuid, {'state': 'SUCCEEDED'})
                 self.assertEqual(self.context, action_plan._context)
 
     def test_refresh(self):