LUCENE-4796, SOLR-4373: Fix concurrency issue in NamedSPILoader and AnalysisSPILoader when doing concurrent core loads in multicore Solr configs


git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1450275 13f79535-47bb-0310-9956-ffa450edef68