Fix flight service IT.

Address ff contant nit.

Signed-off-by: Finn Carroll <[email protected]>

Author: finnegancarroll

plugins/arrow-flight-rpc/src/test/java/org/opensearch/arrow/flight/bootstrap/FlightServiceTests.java

@@ -148,6 +148,7 @@ public void testLifecycleStateTransitions() throws Exception {
     @Override
     public void tearDown() throws Exception {
         super.tearDown();
+        ffLock.close();
     }
 
     private DiscoveryNode createNode(int port) throws Exception {

server/src/main/java/org/opensearch/common/util/FeatureFlags.java

@@ -28,8 +28,8 @@
  */
 public class FeatureFlags {
     // Prefixes public for testing
-    public static final String OS_EXPERIMENTAL_PREFIX = "opensearch.experimental.";
-    public static final String FEATURE_FLAG_PREFIX = OS_EXPERIMENTAL_PREFIX + "feature.";
+    private static final String OS_EXPERIMENTAL_PREFIX = "opensearch.experimental.";
+    static final String FEATURE_FLAG_PREFIX = OS_EXPERIMENTAL_PREFIX + "feature.";
 
     /**
      * Gates the visibility of the remote store to docrep migration.