FOCUS-5620: extend basic authentication (SOLR-4470) to work with solr.xml legacy mode.
FOCUS-5624: If system property 'urlScheme' is set (to '<value>') and /clusterprops.json does not exist in ZooKeeper, the ZkController constructor will now create /clusterprops.json in ZooKeeper with contents '{"urlScheme":"<value>"}'
FOCUS-5625: Some distributed requests were missing auth credentials
SOLR-4470: fix test bug assuming url scheme is always 'http'