[improve][broker] Optimize the logic of terminating system topic (apache#17210)

Author: yuruguo

pulsar-broker/src/main/java/org/apache/pulsar/broker/admin/impl/PersistentTopicsBase.java

@@ -3675,6 +3675,11 @@ protected CompletableFuture<Void> internalRemoveMaxConsumers(boolean isGlobal) {
     }
 
     protected CompletableFuture<MessageId> internalTerminateAsync(boolean authoritative) {
+        if (SystemTopicNames.isSystemTopic(topicName)) {
+            return FutureUtil.failedFuture(new RestException(Status.METHOD_NOT_ALLOWED,
+                    "Termination of a system topic is not allowed"));
+        }
+
         CompletableFuture<Void> ret;
         if (topicName.isGlobal()) {
             ret = validateGlobalNamespaceOwnershipAsync(namespaceName);
@@ -3689,10 +3694,6 @@ protected CompletableFuture<MessageId> internalTerminateAsync(boolean authoritat
                         throw new RestException(Status.METHOD_NOT_ALLOWED,
                                 "Termination of a partitioned topic is not allowed");
                     }
-                    if (SystemTopicNames.isSystemTopic(topicName)) {
-                        throw new RestException(Status.METHOD_NOT_ALLOWED,
-                                "Termination of a system topic is not allowed");
-                    }
                 })
                 .thenCompose(__ -> getTopicReferenceAsync(topicName))
                 .thenCompose(topic -> {