Moved back-ported items to 4.10.3 section

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/branch_5x@1642734 13f79535-47bb-0310-9956-ffa450edef68
SOLR-6726: better strategy for selecting the JMX RMI port based on SOLR_PORT in bin/solr

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/branch_5x@1642747 13f79535-47bb-0310-9956-ffa450edef68