Added 'dummy' entrypoint within watcher_strategies

This should make our 'dummy' strategy available for use.
I also removed all previously defined default goals, which means
that they will have to define it themselves from now on.
This can also be useful for future integration tests.

Change-Id: I6c43eba941022a88851a199b56a6c20f017b9e71
DocImpact
Closes-Bug: #1520178

watcher/tests/api/v1/test_audit_templates.py

@@ -379,7 +379,7 @@ class TestPost(api_base.FunctionalTest):
             wraps=self.dbapi.create_audit_template
         ) as cn_mock:
             audit_template_dict = api_utils.audit_template_post_data(
-                goal='SERVERS_CONSOLIDATION')
+                goal='DUMMY')
             response = self.post_json('/audit_templates', audit_template_dict)
             self.assertEqual(audit_template_dict['goal'],
                              response.json['goal'])