commit changes after doRandomForceMerge, or otherwise they're lost

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/branch_4x@1607779 13f79535-47bb-0310-9956-ffa450edef68
LUCENE-5801: rename test vars, class and add missing ctor

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/branch_4x@1607782 13f79535-47bb-0310-9956-ffa450edef68