SOLR-6402: OverseerCollectionProcessor should not exit for ZooKeeper ConnectionLoss.

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/branch_4x@1619643 13f79535-47bb-0310-9956-ffa450edef68
LUCENE-5672: Fix addIndexes to call maybeMerge

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/branch_4x@1619646 13f79535-47bb-0310-9956-ffa450edef68