Use more specific service name

Author: andrewor14

core/src/main/scala/org/apache/spark/SparkEnv.scala

@@ -146,9 +146,9 @@ object SparkEnv extends Logging {
     }
 
     val securityManager = new SecurityManager(conf)
-
-    val (actorSystem, boundPort) = AkkaUtils.createActorSystem("spark", hostname, port, conf = conf,
-      securityManager = securityManager)
+    val actorSystemName = if (isDriver) "driver actor" else "executor actor"
+    val (actorSystem, boundPort) = AkkaUtils.createActorSystem(
+      actorSystemName, hostname, port, conf, securityManager)
 
     // Figure out which port Akka actually bound to in case the original port is 0 or occupied.
     // This is so that we tell the executors the correct port to connect to.