LUCENE-5889: add missing javadocs

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/branch_4x@1620182 13f79535-47bb-0310-9956-ffa450edef68
SOLR-6424: The hdfs block cache BLOCKCACHE_WRITE_ENABLED is not defaulting to false like it should.
May be related to the SOLR-6423 fail.

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/branch_4x@1620183 13f79535-47bb-0310-9956-ffa450edef68
SOLR-6390: CloudSolrServer constructor improvements. (merge trunk r1620146)


git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/branch_4x@1620185 13f79535-47bb-0310-9956-ffa450edef68