SOLR-2548: Simplified multi-threading of facet.threads logic

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1523677 13f79535-47bb-0310-9956-ffa450edef68
SOLR-5150: HdfsIndexInput may not fully read requested bytes.

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1523693 13f79535-47bb-0310-9956-ffa450edef68