Fix placement_client group help docs generation

To get the placement_client OptGroup help text to generate
in the docs, we have to use the OptGroup object in the
list_opts() method rather than a string for the group name.

https://docs.openstack.org/oslo.config/latest/cli/generator.html#defining-option-discovery-entry-points

Change-Id: Ie728081caa205ded2435c6b95f5e8d4bbd23372c

watcher/conf/placement_client.py

@@ -38,4 +38,4 @@ def register_opts(conf):
 
 
 def list_opts():
-    return [(placement_group.name, placement_opts)]
+    return [(placement_group, placement_opts)]

watcher/tests/conf/test_list_opts.py

@@ -16,6 +16,7 @@
 # limitations under the License.
 
 import mock
+from oslo_config import cfg
 from stevedore import extension
 
 from watcher.conf import opts
@@ -74,7 +75,10 @@ class TestListOpts(base.TestCase):
             result = opts.list_opts()
 
         self.assertIsNotNone(result)
-        for section_name, options in result:
+        for name_or_group, options in result:
+            section_name = name_or_group
+            if isinstance(name_or_group, cfg.OptGroup):
+                section_name = name_or_group.name
             self.assertIn(section_name, expected_sections)
             self.assertTrue(len(options))
 
@@ -106,7 +110,10 @@ class TestListOpts(base.TestCase):
             result = opts.list_opts()
 
         self.assertIsNotNone(result)
-        for section_name, options in result:
+        for name_or_group, options in result:
+            section_name = name_or_group
+            if isinstance(name_or_group, cfg.OptGroup):
+                section_name = name_or_group.name
             self.assertIn(section_name, expected_sections)
             self.assertTrue(len(options))