Quite akka when remote lifecycle logging is disabled.

I noticed when connecting to a standalone cluster Spark gives a bunch
of Akka ERROR logs that make it seem like something is failing.

This patch does two things:

1. Akka dead letter logging is turned on/off according to the existing
   lifecycle spark property.
2. We explicitly silence akka's EndpointWriter log in log4j. This is necessary
   because for some reason that log doesn't pick up on the lifecycle
   logging settings. After a few hours of debugging this was the only solution
   I found that worked.

core/src/main/scala/org/apache/spark/util/AkkaUtils.scala

@@ -21,6 +21,8 @@ import scala.concurrent.duration.{Duration, FiniteDuration}
 
 import akka.actor.{ActorSystem, ExtendedActorSystem, IndestructibleActorSystem}
 import com.typesafe.config.ConfigFactory
+import org.apache.log4j.{Level, Logger}
+
 import org.apache.spark.SparkConf
 
 /**
@@ -47,8 +49,13 @@ private[spark] object AkkaUtils {
     val akkaTimeout = conf.get("spark.akka.timeout", "100").toInt
 
     val akkaFrameSize = conf.get("spark.akka.frameSize", "10").toInt
-    val lifecycleEvents =
-      if (conf.get("spark.akka.logLifecycleEvents", "false").toBoolean) "on" else "off"
+    val akkaLogLifecycleEvents = conf.get("spark.akka.logLifecycleEvents", "false").toBoolean
+    val lifecycleEvents = if (akkaLogLifecycleEvents) "on" else "off"
+    if (!akkaLogLifecycleEvents) {
+      Option(Logger.getLogger("akka.remote.EndpointWriter")).map(l => l.setLevel(Level.FATAL))
+    }
+
+    val logAkkaConfig = if (conf.get("spark.akka.logAkkaConfig", "false").toBoolean) "on" else "off"
 
     val akkaHeartBeatPauses = conf.get("spark.akka.heartbeat.pauses", "600").toInt
     val akkaFailureDetector =
@@ -73,7 +80,10 @@ private[spark] object AkkaUtils {
       |akka.remote.netty.tcp.maximum-frame-size = ${akkaFrameSize}MiB
       |akka.remote.netty.tcp.execution-pool-size = $akkaThreads
       |akka.actor.default-dispatcher.throughput = $akkaBatchSize
+      |akka.log-config-on-start = $logAkkaConfig
       |akka.remote.log-remote-lifecycle-events = $lifecycleEvents
+      |akka.log-dead-letters = $lifecycleEvents
+      |akka.log-dead-letters-during-shutdown = $lifecycleEvents
       """.stripMargin)
 
     val actorSystem = if (indestructible) {