SOLR-4451: SolrJ, and SolrCloud internals, now use SystemDefaultHttpClient under the covers -- allowing many HTTP connection related properties to be controlled via 'standard' java system properties. (merge r1445945)

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/branch_4x@1445955 13f79535-47bb-0310-9956-ffa450edef68