Make BulkProcessorRetryIT less sensitive

In this commit we increase the queue size of the bulk pool in
BulkProcessorRetryIT to make it less sensitive.

As this test case should stress the pool so bulk processor needs to
back off but not so much that the backoff policy will give up at
some point (which is a valid condition), we still keep it below the
default queue size of 50.

core/src/test/java/org/elasticsearch/action/bulk/BulkProcessorRetryIT.java

@@ -54,7 +54,7 @@ public class BulkProcessorRetryIT extends ESIntegTestCase {
                 //.put("threadpool.listener.queue_size", 1)
                 .put("threadpool.get.queue_size", 1)
                 // default is 50
-                .put("threadpool.bulk.queue_size", 20)
+                .put("threadpool.bulk.queue_size", 30)
                 .build();
     }