Support for Metadata Definition Catalog for Tags

This set provides API and shell commands support for:
- CRUD on metadef_tags;

Change-Id: I09bdf43edee6fff615d223f1a6df7c15a1e40565
Implements: blueprint metadefs-tags-cli
DocImpact

glanceclient/v2/client.py

@@ -56,5 +56,8 @@ class Client(object):
         self.metadefs_object = (
             metadefs.ObjectController(self.http_client, self.schemas))
 
+        self.metadefs_tag = (
+            metadefs.TagController(self.http_client, self.schemas))
+
         self.metadefs_namespace = (
             metadefs.NamespaceController(self.http_client, self.schemas))