Check that delete index request succeeded in test teardown (#38903) (#38914)

Backport of #38903

When tearing down from `ESSingleNodeTestCase` we perform a delete on "*"
indices, it some cases, however, those indices are not fully deleted. Rather
than have a failure occur later down the change (see:
#30290 (comment) )
the failure should occurr immediately so it can be diagnosed more easily.

Author: dakrone

test/framework/src/main/java/org/elasticsearch/test/ESSingleNodeTestCase.java

@@ -30,6 +30,7 @@
 import org.elasticsearch.cluster.metadata.MetaData;
 import org.elasticsearch.cluster.routing.allocation.DiskThresholdSettings;
 import org.elasticsearch.common.Priority;
+import org.elasticsearch.common.Strings;
 import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.common.unit.TimeValue;
 import org.elasticsearch.common.util.BigArrays;
@@ -127,6 +128,9 @@ public void tearDown() throws Exception {
                 metaData.persistentSettings().size(), equalTo(0));
         assertThat("test leaves transient cluster metadata behind: " + metaData.transientSettings().keySet(),
                 metaData.transientSettings().size(), equalTo(0));
+        GetIndexResponse indices = client().admin().indices().prepareGetIndex().addIndices("*").get();
+        assertThat("test leaves indices that were not deleted: " + Strings.arrayToCommaDelimitedString(indices.indices()),
+            indices.indices(), equalTo(Strings.EMPTY_ARRAY));
         if (resetNodeAfterTest()) {
             assert NODE != null;
             stopNode();