[SPARK-18490][SQL] duplication nodename extrainfo for ShuffleExchange

## What changes were proposed in this pull request?

   In ShuffleExchange, the nodename's extraInfo are the same when exchangeCoordinator.isEstimated
 is true or false.

Merge the two situation in the PR.

Author: root <root@iZbp1gsnrlfzjxh82cz80vZ.(none)>

Closes #15920 from windpiger/DupNodeNameShuffleExchange.

(cherry picked from commit b0aa1aa1)
Signed-off-by: Sean Owen <sowen@cloudera.com>

sql/core/src/main/scala/org/apache/spark/sql/execution/exchange/ShuffleExchange.scala

@@ -45,9 +45,7 @@ case class ShuffleExchange(
 
   override def nodeName: String = {
     val extraInfo = coordinator match {
-      case Some(exchangeCoordinator) if exchangeCoordinator.isEstimated =>
-        s"(coordinator id: ${System.identityHashCode(coordinator)})"
-      case Some(exchangeCoordinator) if !exchangeCoordinator.isEstimated =>
+      case Some(exchangeCoordinator) =>
         s"(coordinator id: ${System.identityHashCode(coordinator)})"
       case None => ""
     }