Merged revision(s) 1450275 from lucene/dev/trunk:
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/branches/branch_4x@1450276 13f79535-47bb-0310-9956-ffa450edef68