SOLR-6801 Load RequestHandler from blob store

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1646964 13f79535-47bb-0310-9956-ffa450edef68
NPE in tests http://jenkins.thetaphi.de/job/Lucene-Solr-5.x-Linux/11610/

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1646989 13f79535-47bb-0310-9956-ffa450edef68