SOLR-6268: HdfsUpdateLog has a race condition that can expose a closed HDFS FileSystem instance and should close it's FileSystem instance if either inherited close method is called.

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/branch_4x@1619404 13f79535-47bb-0310-9956-ffa450edef68