SOLR-3622, SOLR-5847, SOLR-6194, SOLR-6269: Several DIH fixes/improvements

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1613406 13f79535-47bb-0310-9956-ffa450edef68
SOLR-6269

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1613619 13f79535-47bb-0310-9956-ffa450edef68
tests: null out static

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1613652 13f79535-47bb-0310-9956-ffa450edef68
SOLR-6231: Increased timeouts and hardened the RollingRestartTest

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1613834 13f79535-47bb-0310-9956-ffa450edef68
SOLR-6286: Add logging on how long we slept and how many docs were found

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1613838 13f79535-47bb-0310-9956-ffa450edef68