Code review comment for lp:~rackspace-titan/nova/glance_xen_plugin_preserve_headers

Looks good, thanks for the fix Dan.

Aside:

It's really too bad we have to do this. We're planning to decouple the API from the Registry so that the API will no longer have to handle metadata.

Perhaps in that effort we can have the Registry use the "PATCH" HTTP method so we don't have to pass back the entire metadata structure; instead, we'd only pass the metadata items that were changing.