Add Task.status index to the model

Summary: Informs the model of the index added in D233244.

Test Plan: None

Reviewers: naphat

Reviewed By: naphat

Subscribers: changesbot, anupc

Differential Revision: https://tails.corp.dropbox.com/D233384

changes/models/task.py

@@ -42,6 +42,7 @@ class Task(db.Model):
         Index('idx_task_child_id', 'child_id', 'task_name'),
         Index('idx_task_date_created', 'date_created'),
         UniqueConstraint('task_name', 'parent_id', 'child_id', name='unq_task_entity'),
+        Index('idx_task_status', 'status'),
     )
 
     id = Column(GUID, primary_key=True, default=uuid.uuid4)