test using compound file format, see UseCompoundFile in

https://cwiki.apache.org/confluence/display/solr/IndexConfig+in+SolrConfig
This appears to be necessary as many times a
java.io.FileNotFoundException: (Too many open files) appears.
See also: https://issues.apache.org/jira/browse/SOLR-4 and desperate
users at
http://stackoverflow.com/questions/3828343/too-many-open-file-exception-while-indexin-using-solr
We cannot force users to do a "ulimit -n 1000000", so this action seems
to be required.

defaults/solr/solrconfig.xml

@@ -138,7 +138,7 @@
         <!-- Expert: Enabling compound file will use less files for the index,
          using fewer file descriptors on the expense of performance decrease.
          Default in Lucene is "true". Default in Solr is "false" (since 3.6) -->
-        <!-- <useCompoundFile>false</useCompoundFile> -->
+        <!-- <useCompoundFile>true</useCompoundFile> -->
         
         <!-- ramBufferSizeMB sets the amount of RAM that may be used by Lucene
          indexing for buffering added documents and deletions before they are