Revert "Fix a thread-safety issue in "local" mode."

This reverts commit f26556b.

Conflicts:
	core/src/main/scala/org/apache/spark/executor/Executor.scala

Author: Marcelo Vanzin

core/src/main/scala/org/apache/spark/executor/Executor.scala

@@ -43,18 +43,9 @@ private[spark] class Executor(
     executorId: String,
     executorHostname: String,
     env: SparkEnv,
-    conf: SparkConf,
     isLocal: Boolean = false)
   extends Logging
 {
-
-  def this(executorId: String,
-      slaveHostname: String,
-      env: SparkEnv,
-      isLocal: Boolean = false) = {
-    this(executorId, slaveHostname, env, env.conf, isLocal)
-  }
-
   logInfo(s"Starting executor ID $executorId on host $executorHostname")
 
   // Application dependencies (added through SparkContext) that we've fetched so far on this node.
@@ -64,6 +55,8 @@ private[spark] class Executor(
 
   private val EMPTY_BYTE_BUFFER = ByteBuffer.wrap(new Array[Byte](0))
 
+  private val conf = env.conf
+
   @volatile private var isStopped = false
 
   // No ip or host:port - just hostname

core/src/main/scala/org/apache/spark/scheduler/local/LocalBackend.scala

@@ -21,7 +21,7 @@ import java.nio.ByteBuffer
 
 import akka.actor.{Actor, ActorRef, Props}
 
-import org.apache.spark.{Logging, SparkConf, SparkContext, SparkEnv, TaskState}
+import org.apache.spark.{Logging, SparkContext, SparkEnv, TaskState}
 import org.apache.spark.TaskState.TaskState
 import org.apache.spark.executor.{Executor, ExecutorBackend}
 import org.apache.spark.scheduler.{SchedulerBackend, TaskSchedulerImpl, WorkerOffer}
@@ -43,7 +43,6 @@ private case class StopExecutor()
 private[spark] class LocalActor(
     scheduler: TaskSchedulerImpl,
     executorBackend: LocalBackend,
-    conf: SparkConf,
     private val totalCores: Int)
   extends Actor with ActorLogReceive with Logging {
 
@@ -53,7 +52,7 @@ private[spark] class LocalActor(
   private val localExecutorHostname = "localhost"
 
   private val executor = new Executor(
-    localExecutorId, localExecutorHostname, SparkEnv.get, conf, isLocal = true)
+    localExecutorId, localExecutorHostname, SparkEnv.get, isLocal = true)
 
   override def receiveWithLogging = {
     case ReviveOffers =>
@@ -92,12 +91,11 @@ private[spark] class LocalBackend(scheduler: TaskSchedulerImpl, val totalCores:
   extends SchedulerBackend with ExecutorBackend {
 
   private val appId = "local-" + System.currentTimeMillis
-  private val conf = SparkEnv.get.conf.clone()
   var localActor: ActorRef = null
 
   override def start() {
     localActor = SparkEnv.get.actorSystem.actorOf(
-      Props(new LocalActor(scheduler, this, conf, totalCores)),
+      Props(new LocalActor(scheduler, this, totalCores)),
       "LocalBackendActor")
   }