Add service supervisor

This patch set adds supervisor mechanism for Watcher services
to get ability to track states.

Partially-Implements: blueprint watcher-service-list
Change-Id: Iab1cefb971c79ed27b22b6a5d1bed8698e35f9a4

watcher/tests/api/test_root.py

@@ -37,7 +37,8 @@ class TestV1Root(base.FunctionalTest):
         not_resources = ('id', 'links', 'media_types')
         actual_resources = tuple(set(data.keys()) - set(not_resources))
         expected_resources = ('audit_templates', 'audits', 'actions',
-                              'action_plans', 'scoring_engines')
+                              'action_plans', 'scoring_engines',
+                              'services')
         self.assertEqual(sorted(expected_resources), sorted(actual_resources))
 
         self.assertIn({'type': 'application/vnd.openstack.watcher.v1+json',