SOLR-17088: Fix custom solr.xml usage in tests with extra jettys (#2437)

Author: HoustonPutman

solr/test-framework/src/java/org/apache/solr/cloud/MiniSolrCloudCluster.java

@@ -162,6 +162,7 @@ public class MiniSolrCloudCluster {
   private final Path baseDir;
   private CloudSolrClient solrClient;
   private final JettyConfig jettyConfig;
+  private final String solrXml;
   private final boolean trackJettyMetrics;
 
   private final AtomicInteger nodeIds = new AtomicInteger();
@@ -276,6 +277,7 @@ public MiniSolrCloudCluster(
     Objects.requireNonNull(securityJson);
     this.baseDir = Objects.requireNonNull(baseDir);
     this.jettyConfig = Objects.requireNonNull(jettyConfig);
+    this.solrXml = solrXml == null ? DEFAULT_CLOUD_SOLR_XML : solrXml;
     this.trackJettyMetrics = trackJettyMetrics;
 
     log.info("Starting cluster of {} servers in {}", numServers, baseDir);
@@ -478,18 +480,18 @@ public JettySolrRunner getJettySolrRunner(int index) {
    *
    * @param name the instance name
    * @param config a JettyConfig for the instance's {@link org.apache.solr.embedded.JettySolrRunner}
-   * @param solrXml the string content of the solr.xml file to use, or null to just use default
+   * @param solrXml the string content of the solr.xml file to use, or null to just use the
+   *     cluster's default
    * @return a JettySolrRunner
    */
   public JettySolrRunner startJettySolrRunner(String name, JettyConfig config, String solrXml)
       throws Exception {
-    // tell solr node to look in zookeeper for solr.xml
     final Properties nodeProps = new Properties();
     nodeProps.setProperty("zkHost", zkServer.getZkAddress());
 
     Path runnerPath = createInstancePath(name);
     if (solrXml == null) {
-      solrXml = DEFAULT_CLOUD_SOLR_XML;
+      solrXml = this.solrXml;
     }
     Files.write(runnerPath.resolve("solr.xml"), solrXml.getBytes(StandardCharsets.UTF_8));
     JettyConfig newConfig = JettyConfig.builder(config).build();