CLucene: Helgrind reported "pthread_mutex_destroy of a locked mutex"

> pthread_mutex_destroy (/usr/src/debug/valgrind-3.9.0/helgrind/hg_intercepts.c:478)
> lucene::util::mutex_thread::~mutex_thread() (workdir/UnpackedTarball/clucene/src/shared/CLucene/config/threads.cpp:179)
> lucene::store::FSDirectory::FSIndexInput::close() (workdir/UnpackedTarball/clucene/src/core/CLucene/store/FSDirectory.cpp:225)
> lucene::index::SegmentInfos::read(lucene::store::Directory*, char const*) (workdir/UnpackedTarball/clucene/src/core/CLucene/index/SegmentInfos.cpp:770)
> lucene::index::IndexFileDeleter::IndexFileDeleter(lucene::store::Directory*, lucene::index::IndexDeletionPolicy*, lucene::index::SegmentInfos*, std::ostream*, lucene::index::DocumentsWriter*) (workdir/UnpackedTarball/clucene/src/core/CLucene/index/IndexFileDeleter.cpp:149)
> lucene::index::IndexWriter::init(lucene::store::Directory*, lucene::analysis::Analyzer*, bool, bool, lucene::index::IndexDeletionPolicy*, bool) (workdir/UnpackedTarball/clucene/src/core/CLucene/index/IndexWriter.cpp:262)
> lucene::index::IndexWriter::IndexWriter(char const*, lucene::analysis::Analyzer*, bool) (workdir/UnpackedTarball/clucene/src/core/CLucene/index/IndexWriter.cpp:158)
> HelpIndexer::indexDocuments() (helpcompiler/source/HelpIndexer.cxx:55)

Change-Id: I19cb9bd49b339d206a624c1f1d3dacdd909f4e25