[jvm-packages] delete all constraints from spark layer about obj and eval metrics and handle error in jvm layer (#4560)

* temp

* prediction part

* remove supported*

* add for test

* fix param name

* add rabit

* update rabit

* return value of rabit init

* eliminate compilation warnings

* update rabit

* shutdown

* update rabit again

* check sparkcontext shutdown

* fix logic

* sleep

* fix tests

* test with relaxed threshold

* create new thread each time

* stop for job quitting

* udpate rabit

* update rabit

* update rabit

* update git modules

jvm-packages/xgboost4j-spark/src/main/scala/org/apache/spark/SparkParallelismTracker.scala

@@ -17,6 +17,7 @@
 package org.apache.spark
 
 import java.net.URL
+import java.util.concurrent.atomic.AtomicBoolean
 
 import org.apache.commons.logging.LogFactory
 
@@ -123,18 +124,30 @@ private[spark] class TaskFailedListener extends SparkListener {
       case taskEndReason: TaskFailedReason =>
         logger.error(s"Training Task Failed during XGBoost Training: " +
             s"$taskEndReason, stopping SparkContext")
-        // Spark does not allow ListenerThread to shutdown SparkContext so that we have to do it
-        // in a separate thread
-        val sparkContextKiller = new Thread() {
-          override def run(): Unit = {
-            LiveListenerBus.withinListenerThread.withValue(false) {
-              SparkContext.getOrCreate().stop()
-            }
-          }
-        }
-        sparkContextKiller.setDaemon(true)
-        sparkContextKiller.start()
+        TaskFailedListener.startedSparkContextKiller()
       case _ =>
     }
   }
 }
+
+object TaskFailedListener {
+
+  var killerStarted = false
+
+  private def startedSparkContextKiller(): Unit = this.synchronized {
+    if (!killerStarted) {
+      // Spark does not allow ListenerThread to shutdown SparkContext so that we have to do it
+      // in a separate thread
+      val sparkContextKiller = new Thread() {
+        override def run(): Unit = {
+          LiveListenerBus.withinListenerThread.withValue(false) {
+            SparkContext.getOrCreate().stop()
+          }
+        }
+      }
+      sparkContextKiller.setDaemon(true)
+      sparkContextKiller.start()
+      killerStarted = true
+    }
+  }
+}