add missing 4.9.1 [old] back compat index

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1627491 13f79535-47bb-0310-9956-ffa450edef68
get smoke tester properly parsing versions from TestBackCompat

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1627496 13f79535-47bb-0310-9956-ffa450edef68