Add os-start/stop functional negative tests

The negative tests of os-start/stop API are not covered enough
in functional tests. We want to add the conflict tests of when
this API runs in the unexpected state of server.
* Case of os-start API, the server status must be SHUTOFF.
* Case of os-stop API, the server status must be ACTIVE or ERROR.

Change-Id: I1c44ae737ad39bc58dd3ebfd554176d6400fd9fd

nova/tests/functional/test_servers.py

@@ -506,6 +506,48 @@ class ServersTest(ServersTestBase):
         # Cleanup
         self._delete_server(created_server_id)
 
+    def test_stop_start_servers_negative_invalid_state(self):
+        # Create server
+        server = self._build_minimal_create_server_request()
+        created_server = self.api.post_server({"server": server})
+        created_server_id = created_server['id']
+
+        found_server = self._wait_for_state_change(created_server, 'BUILD')
+        self.assertEqual('ACTIVE', found_server['status'])
+
+        # Start server in ACTIVE
+        # NOTE(mkoshiya): When os-start API runs, the server status
+        # must be SHUTOFF.
+        # By returning 409, I want to confirm that the ACTIVE server does not
+        # cause unexpected behavior.
+        post = {'os-start': {}}
+        ex = self.assertRaises(client.OpenStackApiException,
+                               self.api.post_server_action,
+                               created_server_id, post)
+        self.assertEqual(409, ex.response.status_code)
+        self.assertEqual('ACTIVE', found_server['status'])
+
+        # Stop server
+        post = {'os-stop': {}}
+        self.api.post_server_action(created_server_id, post)
+        found_server = self._wait_for_state_change(found_server, 'ACTIVE')
+        self.assertEqual('SHUTOFF', found_server['status'])
+
+        # Stop server in SHUTOFF
+        # NOTE(mkoshiya): When os-stop API runs, the server status
+        # must be ACTIVE or ERROR.
+        # By returning 409, I want to confirm that the SHUTOFF server does not
+        # cause unexpected behavior.
+        post = {'os-stop': {}}
+        ex = self.assertRaises(client.OpenStackApiException,
+                               self.api.post_server_action,
+                               created_server_id, post)
+        self.assertEqual(409, ex.response.status_code)
+        self.assertEqual('SHUTOFF', found_server['status'])
+
+        # Cleanup
+        self._delete_server(created_server_id)
+
 
 class ServersTestV21(ServersTest):
     api_major_version = 'v2.1'