Code review feedback

Author: rxin

core/src/main/scala/org/apache/spark/network/netty/FileServer.scala

@@ -64,6 +64,7 @@ class FileServer(pResolver: PathResolver, private var port: Int) extends Logging
           case e: InterruptedException =>
             logError("File server start got interrupted", e)
         }
+        // NOTE: bootstrap is shutdown in stop()
       }
     }
     blockingThread.setDaemon(true)

core/src/main/scala/org/apache/spark/network/netty/FileServerHandler.scala

@@ -29,7 +29,7 @@ class FileServerHandler(pResolver: PathResolver)
   extends SimpleChannelInboundHandler[String] with Logging {
 
   override def channelRead0(ctx: ChannelHandlerContext, blockIdString: String): Unit = {
-    val blockId: BlockId = BlockId.apply(blockIdString)
+    val blockId: BlockId = BlockId(blockIdString)
     val fileSegment: FileSegment = pResolver.getBlockLocation(blockId)
     if (fileSegment == null) {
       return