[fix][test] Clear MockedPulsarServiceBaseTest fields to prevent test …

…runtime memory leak (apache#22659)

(cherry picked from commit 025354e)
(cherry picked from commit 13f0aae)

pulsar-broker/src/test/java/org/apache/pulsar/broker/auth/MockedPulsarServiceBaseTest.java

@@ -277,13 +277,20 @@ protected final void internalCleanup() throws Exception {
         }
         if (brokerGateway != null) {
             brokerGateway.close();
+            brokerGateway = null;
         }
         if (pulsarTestContext != null) {
             pulsarTestContext.close();
             pulsarTestContext = null;
         }
+
         resetConfig();
         onCleanup();
+
+        // clear fields to avoid test runtime memory leak, pulsarTestContext already handles closing of these instances
+        pulsar = null;
+        mockZooKeeper = null;
+        mockZooKeeperGlobal = null;
     }
 
     protected void onCleanup() {