Fix update_host API response schema

Compute API update host does not necessary
to be return both 'status' and 'maintenance_mode' as required field.

If any one of them are requested to update, then that only will be
returned in response.

Change-Id: I0abb4682c5d3e4c4d52999d0c08d5bd0d5a7910c
diff --git a/tempest/lib/api_schema/response/compute/v2_1/hosts.py b/tempest/lib/api_schema/response/compute/v2_1/hosts.py
index ae70ff1..cae3435 100644
--- a/tempest/lib/api_schema/response/compute/v2_1/hosts.py
+++ b/tempest/lib/api_schema/response/compute/v2_1/hosts.py
@@ -111,6 +111,9 @@
             'status': {'enum': ['enabled', 'disabled']}
         },
         'additionalProperties': False,
-        'required': ['host', 'maintenance_mode', 'status']
+        'anyOf': [
+            {'required': ['host', 'status']},
+            {'required': ['host', 'maintenance_mode']}
+        ]
     }
 }