[SPARK-2886] Use more specific actor system name than "spark"

As of #1777 we log the name of the actor system when it binds to a port. The current name "spark" is super general and does not convey any meaning. For instance, the following line is taken from my driver log after setting `spark.driver.port` to 5001.
```
14/08/13 19:33:29 INFO Remoting: Remoting started; listening on addresses:
[akka.tcp://sparkandrews-mbp:5001]
14/08/13 19:33:29 INFO Remoting: Remoting now listens on addresses:
[akka.tcp://sparkandrews-mbp:5001]
14/08/06 13:40:05 INFO Utils: Successfully started service 'spark' on port 5001.
```
This commit renames this to "sparkDriver" and "sparkExecutor". The goal of this unambitious PR is simply to make the logged information more explicit without introducing any change in functionality.

Author: Andrew Or <andrewor14@gmail.com>

Closes #1810 from andrewor14/service-name and squashes the following commits:

8c459ed [Andrew Or] Use a common variable for driver/executor actor system names
3a92843 [Andrew Or] Change actor name to sparkDriver and sparkExecutor
921363e [Andrew Or] Merge branch 'master' of github.com:apache/spark into service-name
c8c6a62 [Andrew Or] Do not include hyphens in actor name
1c1b42e [Andrew Or] Avoid spaces in akka system name
f644b55 [Andrew Or] Use more specific service name

1 files changed, 5 insertions, 5 deletions

diff --git a/streaming/src/main/scala/org/apache/spark/streaming/receiver/ReceiverSupervisorImpl.scala b/streaming/src/main/scala/org/apache/spark/streaming/receiver/ReceiverSupervisorImpl.scala
index d934b9cbfc..53a3e6200e 100644
--- a/streaming/src/main/scala/org/apache/spark/streaming/receiver/ReceiverSupervisorImpl.scala
+++ b/streaming/src/main/scala/org/apache/spark/streaming/receiver/ReceiverSupervisorImpl.scala
@@ -20,22 +20,21 @@ package org.apache.spark.streaming.receiver
 import java.nio.ByteBuffer
 import java.util.concurrent.atomic.AtomicLong
 
-import scala.collection.mutable.{SynchronizedBuffer, ArrayBuffer}
+import scala.collection.mutable.ArrayBuffer
 import scala.concurrent.Await
 
 import akka.actor.{Actor, Props}
 import akka.pattern.ask
 
+import com.google.common.base.Throwables
+
 import org.apache.spark.{Logging, SparkEnv}
-import org.apache.spark.storage.StreamBlockId
 import org.apache.spark.streaming.scheduler._
 import org.apache.spark.util.{Utils, AkkaUtils}
 import org.apache.spark.storage.StreamBlockId
 import org.apache.spark.streaming.scheduler.DeregisterReceiver
 import org.apache.spark.streaming.scheduler.AddBlock
-import scala.Some
 import org.apache.spark.streaming.scheduler.RegisterReceiver
-import com.google.common.base.Throwables
 
 /**
  * Concrete implementation of [[org.apache.spark.streaming.receiver.ReceiverSupervisor]]
@@ -56,7 +55,8 @@ private[streaming] class ReceiverSupervisorImpl(
   private val trackerActor = {
     val ip = env.conf.get("spark.driver.host", "localhost")
     val port = env.conf.getInt("spark.driver.port", 7077)
-    val url = "akka.tcp://spark@%s:%s/user/ReceiverTracker".format(ip, port)
+    val url = "akka.tcp://%s@%s:%s/user/ReceiverTracker".format(
+      SparkEnv.driverActorSystemName, ip, port)
     env.actorSystem.actorSelection(url)
   }