LUCENE-5908: Backport to 4.10 (merged 1620760)

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/lucene_solr_4_10@1620762 13f79535-47bb-0310-9956-ffa450edef68
SOLR-6437: Managed schema is not enabled with /update/json and /update/json/docs request handlers

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/lucene_solr_4_10@1620771 13f79535-47bb-0310-9956-ffa450edef68