Revisit the fix for CONNECTORS-623.  Override the HttpSolrServer class instead, and force multipart post, in order to guarantee delivery of content type, name, and length to SolrCell.

git-svn-id: https://svn.apache.org/repos/asf/manifoldcf/trunk@1446153 13f79535-47bb-0310-9956-ffa450edef68