MINOR: Improve shutdown sequence

Author: Ismael Juma <ismael@juma.me.uk>

Reviewers: Jun Rao <junrao@gmail.com>

Closes #3030 from ijuma/improve-shutdown-sequence

core/src/main/scala/kafka/server/KafkaServer.scala

@@ -589,28 +589,35 @@ class KafkaServer(val config: KafkaConfig, time: Time = Time.SYSTEM, threadNameP
       if (shutdownLatch.getCount > 0 && isShuttingDown.compareAndSet(false, true)) {
         CoreUtils.swallow(controlledShutdown())
         brokerState.newState(BrokerShuttingDown)
+        
         if (socketServer != null)
           CoreUtils.swallow(socketServer.shutdown())
         if (requestHandlerPool != null)
           CoreUtils.swallow(requestHandlerPool.shutdown())
+
         CoreUtils.swallow(kafkaScheduler.shutdown())
+
         if (apis != null)
           CoreUtils.swallow(apis.close())
         CoreUtils.swallow(authorizer.foreach(_.close()))
-        if (replicaManager != null)
-          CoreUtils.swallow(replicaManager.shutdown())
         if (adminManager != null)
           CoreUtils.swallow(adminManager.shutdown())
+
         if (transactionCoordinator != null)
           CoreUtils.swallow(transactionCoordinator.shutdown())
         if (groupCoordinator != null)
           CoreUtils.swallow(groupCoordinator.shutdown())
+
+        if (replicaManager != null)
+          CoreUtils.swallow(replicaManager.shutdown())
         if (logManager != null)
           CoreUtils.swallow(logManager.shutdown())
+
         if (kafkaController != null)
           CoreUtils.swallow(kafkaController.shutdown())
         if (zkUtils != null)
           CoreUtils.swallow(zkUtils.close())
+
         if (metrics != null)
           CoreUtils.swallow(metrics.close())