Adds a repoducer for post live migration fail

Adds a regression test or repoducer for post live migration
fail at destination, the possible casue can be fail to get
instance network info or  block device info

changes:
adds return server from _live_migrate in _integrated_helpers

Related-Bug: #1628606
Change-Id: I48dbe0aae8a3943fdde69cda1bd663d70ea0eb19
(cherry picked from commit a20baeca1f)
(cherry picked from commit 74a618a811)

nova/tests/functional/integrated_helpers.py

@@ -540,8 +540,9 @@ class InstanceHelperMixin:
         self.api.post_server_action(
             server['id'],
             {'os-migrateLive': {'host': None, 'block_migration': 'auto'}})
-        self._wait_for_state_change(server, server_expected_state)
+        server = self._wait_for_state_change(server, server_expected_state)
         self._wait_for_migration_status(server, [migration_expected_state])
+        return server
 
     _live_migrate_server = _live_migrate
 

nova/tests/functional/regressions/test_bug_1628606.py

@@ -0,0 +1,61 @@
+# Licensed under the Apache License, Version 2.0 (the "License"); you may
+# not use this file except in compliance with the License. You may obtain
+# a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+# License for the specific language governing permissions and limitations
+# under the License.
+
+from nova import test
+from nova.tests import fixtures as nova_fixtures
+from nova.tests.functional.api import client
+from nova.tests.functional import fixtures as func_fixtures
+from nova.tests.functional import integrated_helpers
+from unittest import mock
+
+
+class PostLiveMigrationFail(
+    test.TestCase, integrated_helpers.InstanceHelperMixin):
+    """Regression test for bug 1628606
+    """
+
+    def setUp(self):
+        super().setUp()
+        self.useFixture(nova_fixtures.NeutronFixture(self))
+        self.glance = self.useFixture(nova_fixtures.GlanceFixture(self))
+        self.useFixture(func_fixtures.PlacementFixture())
+        self.useFixture(nova_fixtures.HostNameWeigherFixture())
+
+        self.start_service('conductor')
+        self.start_service('scheduler')
+
+        api_fixture = self.useFixture(nova_fixtures.OSAPIFixture(
+            api_version='v2.1'))
+
+        self.api = api_fixture.admin_api
+        self.api.microversion = 'latest'
+
+        self.src = self._start_compute(host='host1')
+        self.dest = self._start_compute(host='host2')
+
+    @mock.patch(
+        'nova.compute.manager.ComputeManager'
+        '._post_live_migration_remove_source_vol_connections')
+    def test_post_live_migration(self, mock_migration):
+        server = self._create_server(networks=[])
+        self.assertEqual(self.src.host, server['OS-EXT-SRV-ATTR:host'])
+
+        error = client.OpenStackApiException(
+            "Failed to remove source vol connection post live migration")
+        mock_migration.side_effect = error
+
+        server = self._live_migrate(
+            server, migration_expected_state='error',
+            server_expected_state='ERROR')
+        # FIXME(amit): this should point to the dest as after migration
+        # but does not because of bug 1628606
+        self.assertEqual(self.src.host, server['OS-EXT-SRV-ATTR:host'])