Fix ReloadSynonymAnalyzerIT failure (#53663)

There is an assertion in ReloadAnalyzersResponse.merge that compares index names
of merged responses that was falsely using object equality instead of
String.equals(). In the past this didn't seem to matter but with changes in the
test setup we started to see failures. Correcting this and also simplifying test
a bit to be able to run it repeatedly if needed.

Closes #53443

x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/action/ReloadAnalyzersResponse.java

@@ -164,7 +164,7 @@ public Set<String> getReloadedAnalyzers() {
         }
 
         void merge(ReloadResult other) {
-            assert this.indexName == other.index;
+            assert this.indexName.equals(other.index);
             this.reloadedAnalyzers.addAll(other.reloadedSearchAnalyzers);
             this.reloadedIndicesNodes.add(other.nodeId);
         }

x-pack/plugin/core/src/test/java/org/elasticsearch/xpack/core/rest/action/ReloadSynonymAnalyzerIT.java

@@ -5,7 +5,6 @@
  */
 package org.elasticsearch.xpack.core.rest.action;
 
-import org.apache.lucene.util.LuceneTestCase;
 import org.elasticsearch.action.admin.indices.analyze.AnalyzeAction.AnalyzeToken;
 import org.elasticsearch.action.admin.indices.analyze.AnalyzeAction.Response;
 import org.elasticsearch.action.search.SearchResponse;
@@ -40,7 +39,6 @@
 import static org.elasticsearch.test.hamcrest.ElasticsearchAssertions.assertHitCount;
 import static org.elasticsearch.test.hamcrest.ElasticsearchAssertions.assertNoFailures;
 
-@LuceneTestCase.AwaitsFix(bugUrl = "https://github.com/elastic/elasticsearch/issues/53443")
 public class ReloadSynonymAnalyzerIT extends ESIntegTestCase {
 
     @Override
@@ -66,10 +64,8 @@ public void testSynonymsUpdateable() throws FileNotFoundException, IOException,
         Path config = internalCluster().getInstance(Environment.class).configFile();
         String synonymsFileName = "synonyms.txt";
         Path synonymsFile = config.resolve(synonymsFileName);
-        Files.createFile(synonymsFile);
-        assertTrue(Files.exists(synonymsFile));
         try (PrintWriter out = new PrintWriter(
-                new OutputStreamWriter(Files.newOutputStream(synonymsFile, StandardOpenOption.CREATE), StandardCharsets.UTF_8))) {
+                new OutputStreamWriter(Files.newOutputStream(synonymsFile), StandardCharsets.UTF_8))) {
             out.println("foo, baz");
         }
         assertAcked(client().admin().indices().prepareCreate("test").setSettings(Settings.builder()