Solr Connector cannot index documents when Solr is protected by authentication

The Solr connector cannot deal with Solr servers that are protected by authentication. The reason is that HttpClient forces a retry based on the WWW-authenticate header that is returned, but the HttpEntity is not resettable and thus the retry fails for that reason.

This is a regression, because the Solr connector used to properly support basic auth, and now no longer does.