api: Address issues with images APIs

Populate missing 'required' values.

Change-Id: I4e1e00c3f7d4f2a581db42dae3535a5931e8f1cc
Signed-off-by: Stephen Finucane <stephenfin@redhat.com>

nova/api/openstack/compute/schemas/images.py

@@ -189,7 +189,7 @@ show_response = {
     'properties': {
         'image': copy.deepcopy(_image_response),
     },
-    'required': [],
+    'required': ['image'],
     'additionalProperties': False,
 }
 
@@ -213,7 +213,7 @@ index_response = {
         },
         'images_links': response_types.collection_links,
     },
-    'required': [],
+    'required': ['images'],
     'additionalProperties': False,
 }