Fix race condition with the object-store relation

The `CONFIGS.write(GLANCE_SWIFT_CONF)` is missing in the object-store
hook. This config file is used when the `swift` backend is enabled.

This bug is only encountered on some deployments, because there are multiple
places where `CONFIGS.write_all()` is called.

If the `object-store` relation is established, and another hook calls
`CONFIGS.write_all()`, this problem wouldn't reproduce. However, if
`object-store` relation is executed last, this issue will pop up.

Closes-Bug: #1915300
Change-Id: Ie52b18fc4dc637dbeec5ecfb8d5930a24c5f72cf

hooks/glance_relations.py

@@ -46,6 +46,7 @@ from glance_utils import (
     CHARM,
     GLANCE_REGISTRY_CONF,
     GLANCE_API_CONF,
+    GLANCE_SWIFT_CONF,
     HAPROXY_CONF,
     ceph_config_file,
     setup_ipv6,
@@ -294,6 +295,9 @@ def object_store_joined():
     [image_service_joined(rid) for rid in relation_ids('image-service')]
     update_image_location_policy(CONFIGS)
     CONFIGS.write(GLANCE_API_CONF)
+    cmp_release = CompareOpenStackReleases(os_release('glance-common'))
+    if cmp_release >= 'mitaka':
+        CONFIGS.write(GLANCE_SWIFT_CONF)
 
 
 @hooks.hook('ceph-relation-joined')

unit_tests/test_glance_relations.py

@@ -294,9 +294,12 @@ class GlanceRelationTests(CharmTestCase):
         configs.complete_contexts.return_value = ['identity-service',
                                                   'object-store']
         configs.write = MagicMock()
+        self.os_release.return_value = 'victoria'
         relations.object_store_joined()
-        self.assertEqual([call('/etc/glance/glance-api.conf')],
-                         configs.write.call_args_list)
+        configs.write.assert_has_calls([
+            call('/etc/glance/glance-api.conf'),
+            call('/etc/glance/glance-swift.conf'),
+        ])
         self.assertTrue(mock_update_image_location_policy.called)
 
     @patch.object(relations, 'update_image_location_policy')