HTTPS Reverse Proxy breaks opensocial container osapi endpoint URLs

When running Nuxeo 5.6 behind an https reverse proxy, the generated opensocial container osapi endpoint URLs (opensocial/social/rpc, opensocial/gadgets/api/rpc) are invalid. As a result, HTTP Error 500 entries appear in the log.

I am not sure if the URLs should have a base URL of nuxeo.loopback.url (with protocol http) or if they should have the external base URL (with protocol https). Currently, the URLs generated have the external base URL with the wrong protocol (http and not https).

See http://answers.nuxeo.com/questions/6120/opensocial-osapi-endpoint-url-protocol-and-https-reverse-proxy.