Enable client V2 to update/delete tags for a given image.

Added the CLI option image-tag-update to associate a tag to an image via API V2.
Added the CLI option image-tag-delete to delete a tag associated with an image via API V2.

Related to bp glance-client-v2

Change-Id: I76060e1982223770a6c2c0bd9376d568af0df456

glanceclient/v2/shell.py

@@ -133,3 +133,31 @@ def do_image_download(gc, args):
 def do_image_delete(gc, args):
     """Delete specified image."""
     gc.images.delete(args.id)
+
+
+@utils.arg('image_id', metavar='<IMAGE_ID>',
+           help='Image to be updated with the given tag')
+@utils.arg('tag_value', metavar='<TAG_VALUE>',
+           help='Value of the tag')
+def do_image_tag_update(gc, args):
+        """Update an image with the given tag."""
+        if not (args.image_id and args.tag_value):
+            utils.exit('Unable to update tag. Specify image_id and tag_value')
+        else:
+            gc.image_tags.update(args.image_id, args.tag_value)
+            image = gc.images.get(args.image_id)
+            image = [image]
+            columns = ['ID', 'Tags']
+            utils.print_list(image, columns)
+
+
+@utils.arg('image_id', metavar='<IMAGE_ID>',
+           help='Image whose tag to be deleted')
+@utils.arg('tag_value', metavar='<TAG_VALUE>',
+           help='Value of the tag')
+def do_image_tag_delete(gc, args):
+    """Delete the tag associated with the given image."""
+    if not (args.image_id and args.tag_value):
+        utils.exit('Unable to delete tag. Specify image_id and tag_value')
+    else:
+        gc.image_tags.delete(args.image_id, args.tag_value)