SOLR-6410: Ensure all Lookup instances are closed via CloseHook - move CHANGES.txt entry for 4.10 backport (merge r1620674)

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/branch_4x@1620675 13f79535-47bb-0310-9956-ffa450edef68