SOLR-5244: Exporting Full Sorted Result Sets

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1619783 13f79535-47bb-0310-9956-ffa450edef68
SOLR-6402: Only exit the thread loop on a KeeperException if it's expiration.

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1619792 13f79535-47bb-0310-9956-ffa450edef68