apache/spark — pull request #3648 by ilayaperumalg (2014-12-09 21:15:13+00:00)
Title: [SPARK-4803] Remove duplicate RegisterReceiver message

- The ReceiverTracker receivers `RegisterReceiver` messages two times
1) When the actor at `ReceiverSupervisorImpl`'s preStart is invoked
2) After the receiver is started at the executor `onReceiverStart()` at `ReceiverSupervisorImpl`

Though, RegisterReceiver message uses the same streamId and the receiverInfo gets updated everytime
the message is processed at the `ReceiverTracker`, it makes sense to call register receiver only after the
receiver is started.