Apply expected patch format when updating tags in v2.images

Currently, glanceclient.v2.update builds a patch request that does not
match glance API.

This patch overrides the default behaviour to customize the patch
request with the right format for the API.

Co-Authored-By: Steve Lewis <steve.lewis@rackspace.com>
Fixes bug 1306774
Change-Id: If0739ac285da1e741bfa40b6c719331a5ce49319

glanceclient/v2/schemas.py

@@ -14,6 +14,7 @@
 #    under the License.
 
 import copy
+import json
 import jsonpatch
 import six
 import warlock.model as warlock
@@ -29,18 +30,35 @@ class SchemaBasedModel(warlock.Model):
     expects.
     """
 
+    def _make_custom_patch(self, new, original):
+        if not self.get('tags'):
+            tags_patch = []
+        else:
+            tags_patch = [{"path": "/tags",
+                          "value": self.get('tags'),
+                          "op": "replace"}]
+
+        patch_string = jsonpatch.make_patch(original, new).to_string()
+        patch = json.loads(patch_string)
+        if not patch:
+            return json.dumps(tags_patch)
+        else:
+            return json.dumps(patch + tags_patch)
+
     @warlock.Model.patch.getter
     def patch(self):
         """Return a jsonpatch object representing the delta."""
         original = copy.deepcopy(self.__dict__['__original__'])
         new = dict(self)
-        if self.__dict__['schema']:
+        if self.schema:
             for (name, prop) in six.iteritems(self.schema['properties']):
                 if (name not in original and name in new and
                         prop.get('is_base', True)):
                     original[name] = None
 
-        return jsonpatch.make_patch(original, dict(self)).to_string()
+        original['tags'] = None
+        new['tags'] = None
+        return self._make_custom_patch(new, original)
 
 
 class SchemaProperty(object):