fix excessive file handle usage in test

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1670934 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/lucene/core/src/test/org/apache/lucene/index/TestIndexWriterDelete.java b/lucene/core/src/test/org/apache/lucene/index/TestIndexWriterDelete.java
index 771f5d4..b9cf3c6 100644
--- a/lucene/core/src/test/org/apache/lucene/index/TestIndexWriterDelete.java
+++ b/lucene/core/src/test/org/apache/lucene/index/TestIndexWriterDelete.java
@@ -1130,7 +1130,9 @@
                                        .setRAMBufferSizeMB(0.5)
                                        .setMaxBufferedDocs(-1)
                                        .setMergePolicy(NoMergePolicy.INSTANCE)
-                                       .setReaderPooling(false)) {
+                                       .setReaderPooling(false)
+                                       // always use CFS so we don't use tons of file handles in the test
+                                       .setUseCompoundFile(true)) {
         @Override
         public void doAfterFlush() {
           assertTrue("only " + docsInSegment.get() + " in segment", closing.get() || docsInSegment.get() >= 7);