Fix unintentional changes

Author: zsxwing

streaming/src/main/scala/org/apache/spark/streaming/receiver/ReceiverSupervisor.scala

@@ -101,7 +101,7 @@ private[streaming] abstract class ReceiverSupervisor(
   protected def onStop(message: String, error: Option[Throwable]) { }
 
   /** Called when receiver is started. Return true if the driver accepts us */
-  protected def onReceiverStart(): Boolean = true
+  protected def onReceiverStart(): Boolean
 
   /** Called when receiver is stopped */
   protected def onReceiverStop(message: String, error: Option[Throwable]) { }

streaming/src/test/scala/org/apache/spark/streaming/ReceiverSuite.scala

@@ -129,18 +129,6 @@ class ReceiverSuite extends TestSuiteBase with Timeouts with Serializable {
     }
   }
 
-  test("restart receiver should consider the scheduled locations") {
-    val receiver = new FakeReceiver
-    val executor = new FakeReceiverSupervisor(receiver)
-    executor.start()
-    receiver.restart("force the receiver restart")
-    eventually(timeout(30000 millis), interval(10 millis)) {
-      // Since the scheduled location is not the current host, the receiver should exit
-      assert(receiver.onStopCalled)
-      assert(receiver.isStopped)
-    }
-  }
-
   test("block generator") {
     val blockGeneratorListener = new FakeBlockGeneratorListener
     val blockIntervalMs = 200