Add 'images_links' attribute in image list schema

Image list and detail list response may have 'images_links' attribute
but schema files for above APIs do not have 'images_links' attribute.

This patch fix the above issue.

Change-Id: I6bb5521063c29e3ba5179613dd77a3f4995c3f27
diff --git a/tempest/api_schema/response/compute/v2/images.py b/tempest/api_schema/response/compute/v2/images.py
index 43dae38..21dc9ab 100644
--- a/tempest/api_schema/response/compute/v2/images.py
+++ b/tempest/api_schema/response/compute/v2/images.py
@@ -78,8 +78,11 @@
                     },
                     'required': ['id', 'links', 'name']
                 }
-            }
+            },
+            'images_links': parameter_types.links
         },
+        # NOTE(gmann): images_links attribute is not necessary to be
+        # present always So it is not 'required'.
         'required': ['images']
     }
 }
@@ -132,8 +135,11 @@
             'images': {
                 'type': 'array',
                 'items': common_image_schema
-            }
+            },
+            'images_links': parameter_types.links
         },
+        # NOTE(gmann): images_links attribute is not necessary to be
+        # present always So it is not 'required'.
         'required': ['images']
     }
 }