Workaround deprecated 1.2 API

[assiotis]

The DBC 1.2 REST API has been deprecated and some of the functionality stopped working. Some of the endpoints that used to return 4xx unauthorized responses, now may return 500. Unfortunately, that means that the Apache HTTP Client does not attempt to authenticate using theAuthorization header (basic HTTP auth), because by design it does not pass that header unless challenged. To fix that, we pass the context around that contains a credentials cache.