[SPARK-16439] Fix number formatting in SQL UI

## What changes were proposed in this pull request?

Spark SQL UI display numbers greater than 1000 with u00A0 as grouping separator.
Problem exists when server locale has no-breaking space as separator. (for example pl_PL)
This patch turns off grouping and remove this separator.

The problem starts with this PR.
https://github.com/apache/spark/pull/12425/files#diff-803f475b01acfae1c5c96807c2ea9ddcR125

## How was this patch tested?

Manual UI tests. Screenshot attached.

![image](https://cloud.githubusercontent.com/assets/4006010/16749556/5cb5a372-47cb-11e6-9a95-67fd3f9d1c71.png)

Author: Maciej Brynski <maciej.brynski@adpilot.pl>

Closes #14142 from maver1ck/master.

sql/core/src/main/scala/org/apache/spark/sql/execution/metric/SQLMetrics.scala

@@ -101,7 +101,9 @@ private[sql] object SQLMetrics {
    */
   def stringValue(metricsType: String, values: Seq[Long]): String = {
     if (metricsType == SUM_METRIC) {
-      NumberFormat.getInstance().format(values.sum)
+      val numberFormat = NumberFormat.getInstance()
+      numberFormat.setGroupingUsed(false)
+      numberFormat.format(values.sum)
     } else {
       val strFormat: Long => String = if (metricsType == SIZE_METRIC) {
         Utils.bytesToString