DistributedSegmentReadLocker should be allowed to skip ReadLocks on small files

Both of these methods:

• org.infinispan.lucene.readlocks.DistributedSegmentReadLocker.deleteOrReleaseReadLock(String)
• org.infinispan.lucene.readlocks.DistributedSegmentReadLocker.realFileDelete(FileReadLockKey, AdvancedCache<Object, Integer>, AdvancedCache<?, ?>, AdvancedCache<?, ?>, boolean)

Are performing a lot of unnecessary operations - potentially on synchronous clustered caches - as we know in advance that files which are not being chunked don't need a read lock, and are not being chunked in smaller pieces (which affects how we delete things).

The determining factor between the two styles is defined in:
org.infinispan.lucene.impl.DirectoryLuceneV4.openInput(String, IOContext)

   @Override
   public IndexInput openInput(final String name, final IOContext context) throws IOException {
      final IndexInputContext indexInputContext = impl.openInput(name);
      if ( indexInputContext.readLocks == null ) {
         return new SingleChunkIndexInput(indexInputContext);
      }
      else {
         return new InfinispanIndexInput(indexInputContext);
      }
   }