Change the ordering of imports

Author: jerryshao

external/kafka/src/main/scala/org/apache/spark/streaming/kafka/KafkaReceiver.scala

@@ -17,12 +17,12 @@
 
 package org.apache.spark.streaming.kafka
 
-import scala.collection.Map
-import scala.reflect.{classTag, ClassTag}
-
 import java.util.Properties
 import java.util.concurrent.Executors
 
+import scala.collection.Map
+import scala.reflect.{classTag, ClassTag}
+
 import kafka.consumer._
 import kafka.serializer.Decoder
 import kafka.utils.VerifiableProperties