Make set/unset command in volume pass normally when nothing specified

Change-Id: Iac2d1b4ba9fa6358dc9317054af970eae8d49e84

Author: sunyajing

openstackclient/volume/v2/volume.py

@@ -457,6 +457,3 @@ def take_action(self, parsed_args):
         if parsed_args.image_property:
             volume_client.volumes.delete_image_metadata(
                 volume.id, parsed_args.image_property)
-
-        if (not parsed_args.image_property and not parsed_args.property):
-            LOG.error(_("No changes requested"))