avoid NRTCachingDirectory in this test

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1481938 13f79535-47bb-0310-9956-ffa450edef68
remove strange retry-port loop, and just bind to ephemeral port

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1481947 13f79535-47bb-0310-9956-ffa450edef68