Simplify doc creation check in acked indexing test

This commit simplifies the doc creation check while indexing in the
acked indexing test.

core/src/test/java/org/elasticsearch/discovery/DiscoveryWithServiceDisruptionsIT.java

@@ -495,7 +495,7 @@ public class DiscoveryWithServiceDisruptionsIT extends ESIntegTestCase {
                                 logger.trace("[{}] indexing id [{}] through node [{}] targeting shard [{}]", name, id, node, shard);
                                 IndexResponse response =
                                     client.prepareIndex("test", "type", id).setSource("{}").setTimeout(timeout).get(timeout);
-                                assertThat(response.getVersion(), equalTo(1L));
+                                assertTrue("doc [" + id + "] should have been created", response.isCreated());
                                 ackedDocs.put(id, node);
                                 logger.trace("[{}] indexed id [{}] through node [{}]", name, id, node);
                             } catch (ElasticsearchException e) {