[SPARK-24029][CORE] Set SO_REUSEADDR on listen sockets.

This allows sockets to be bound even if there are sockets
from a previous application that are still pending closure. It
avoids bind issues when, for example, re-starting the SHS.

Don't enable the option on Windows though. The following page
explains some odd behavior that this option can have there:
https://msdn.microsoft.com/en-us/library/windows/desktop/ms740621%28v=vs.85%29.aspx

I intentionally ignored server sockets that always bind to
ephemeral ports, since those don't benefit from this option.

Author: Marcelo Vanzin <vanzin@cloudera.com>

Closes #21110 from vanzin/SPARK-24029.

common/network-common/src/main/java/org/apache/spark/network/server/TransportServer.java

@@ -32,6 +32,7 @@
 import io.netty.channel.ChannelOption;
 import io.netty.channel.EventLoopGroup;
 import io.netty.channel.socket.SocketChannel;
+import org.apache.commons.lang3.SystemUtils;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -98,7 +99,8 @@ private void init(String hostToBind, int portToBind) {
       .group(bossGroup, workerGroup)
       .channel(NettyUtils.getServerChannelClass(ioMode))
       .option(ChannelOption.ALLOCATOR, allocator)
-      .childOption(ChannelOption.ALLOCATOR, allocator);
+      .childOption(ChannelOption.ALLOCATOR, allocator)
+      .childOption(ChannelOption.SO_REUSEADDR, !SystemUtils.IS_OS_WINDOWS);
 
     this.metrics = new NettyMemoryMetrics(
       allocator, conf.getModuleName() + "-server", conf);

core/src/main/scala/org/apache/spark/deploy/rest/RestSubmissionServer.scala

@@ -94,6 +94,7 @@ private[spark] abstract class RestSubmissionServer(
       new HttpConnectionFactory())
     connector.setHost(host)
     connector.setPort(startPort)
+    connector.setReuseAddress(!Utils.isWindows)
     server.addConnector(connector)
 
     val mainHandler = new ServletContextHandler

core/src/main/scala/org/apache/spark/ui/JettyUtils.scala

@@ -344,6 +344,7 @@ private[spark] object JettyUtils extends Logging {
           connectionFactories: _*)
         connector.setPort(port)
         connector.setHost(hostName)
+        connector.setReuseAddress(!Utils.isWindows)
 
         // Currently we only use "SelectChannelConnector"
         // Limit the max acceptor number to 8 so that we don't waste a lot of threads