OrcFile#getStaticMemoryManager caches initial configuration and leaks classloaders

  private static synchronized MemoryManager getStaticMemoryManager(
      final Configuration conf) {
    if (memoryManager == null) {
      memoryManager = new ThreadLocal<MemoryManager>() {
        @Override
        protected MemoryManager initialValue() {
          return new MemoryManagerImpl(conf);
        }
      };
    }
    return memoryManager.get();
  }

  private static synchronized MemoryManager getStaticMemoryManager(
      final Configuration conf) {
    MemoryManager manager = memoryManager.get();
    if (manager == null) {
      manager = new MemoryManagerImpl(conf);
      memoryManager.set(manager);
    }
    return manager;
  }