Fix change_nova_service_state action

The function signature has been changed in 2.53 version[1]
and this patch is required to fix watcher-tempest-plugin.
If all tests are ok, I'll merge it ASAP.

[1]: https://developer.openstack.org/api-ref/compute/#enable-scheduling-for-a-compute-service

Change-Id: Ie03519dac2a55263e278344fd00f103067f90f27

doc/source/conf.py

@@ -42,6 +42,7 @@ extensions = [
     'ext.versioned_notifications',
     'oslo_config.sphinxconfiggen',
     'openstackdocstheme',
+    'sphinx.ext.napoleon',
 ]
 
 wsme_protocols = ['restjson']