Fixed build error after merging in master

core/src/main/scala/org/apache/spark/scheduler/cluster/CoarseGrainedClusterMessage.scala

@@ -31,7 +31,7 @@ private[spark] object CoarseGrainedClusterMessages {
   // Driver to executors
   case class LaunchTask(task: TaskDescription) extends CoarseGrainedClusterMessage
 
-  case class KillTask(taskId: Long, executor: String) extends StandaloneClusterMessage
+  case class KillTask(taskId: Long, executor: String) extends CoarseGrainedClusterMessage
 
   case class RegisteredExecutor(sparkProperties: Seq[(String, String)])
     extends CoarseGrainedClusterMessage