Pick random port instead of 4040

Author: andrewor14

core/src/test/scala/org/apache/spark/ui/UISuite.scala

@@ -23,7 +23,6 @@ import javax.servlet.http.HttpServletRequest
 import scala.io.Source
 import scala.util.{Failure, Success, Try}
 
-import org.eclipse.jetty.server.Server
 import org.eclipse.jetty.servlet.ServletContextHandler
 import org.scalatest.FunSuite
 import org.scalatest.concurrent.Eventually._
@@ -108,14 +107,9 @@ class UISuite extends FunSuite {
   }
 
   test("jetty selects different port under contention") {
-    val startPort = 4040
-    val server = new Server(startPort)
+    val server = new ServerSocket(0)
+    val startPort = server.getLocalPort
 
-    Try { server.start() } match {
-      case Success(s) =>
-      case Failure(e) =>
-      // Either case server port is busy hence setup for test complete
-    }
     val serverInfo1 = JettyUtils.startJettyServer(
       "0.0.0.0", startPort, Seq[ServletContextHandler](), new SparkConf)
     val serverInfo2 = JettyUtils.startJettyServer(