[SPARK-20156][CORE][SQL][STREAMING][MLLIB] Java String toLowerCase "Turkish locale bug" causes Spark problems

## What changes were proposed in this pull request?

Add Locale.ROOT to internal calls to String `toLowerCase`, `toUpperCase`, to avoid inadvertent locale-sensitive variation in behavior (aka the "Turkish locale problem").

The change looks large but it is just adding `Locale.ROOT` (the locale with no country or language specified) to every call to these methods.

## How was this patch tested?

Existing tests.

Author: Sean Owen <sowen@cloudera.com>

Closes #17527 from srowen/SPARK-20156.

1 files changed, 2 insertions, 2 deletions

diff --git a/external/kafka-0-8/src/main/scala/org/apache/spark/streaming/kafka/KafkaUtils.scala b/external/kafka-0-8/src/main/scala/org/apache/spark/streaming/kafka/KafkaUtils.scala
index d5aef8184f..78230725f3 100644
--- a/external/kafka-0-8/src/main/scala/org/apache/spark/streaming/kafka/KafkaUtils.scala
+++ b/external/kafka-0-8/src/main/scala/org/apache/spark/streaming/kafka/KafkaUtils.scala
@@ -20,7 +20,7 @@ package org.apache.spark.streaming.kafka
 import java.io.OutputStream
 import java.lang.{Integer => JInt, Long => JLong, Number => JNumber}
 import java.nio.charset.StandardCharsets
-import java.util.{List => JList, Map => JMap, Set => JSet}
+import java.util.{List => JList, Locale, Map => JMap, Set => JSet}
 
 import scala.collection.JavaConverters._
 import scala.reflect.ClassTag
@@ -206,7 +206,7 @@ object KafkaUtils {
       kafkaParams: Map[String, String],
       topics: Set[String]
     ): Map[TopicAndPartition, Long] = {
-    val reset = kafkaParams.get("auto.offset.reset").map(_.toLowerCase)
+    val reset = kafkaParams.get("auto.offset.reset").map(_.toLowerCase(Locale.ROOT))
     val result = for {
       topicPartitions <- kc.getPartitions(topics).right
       leaderOffsets <- (if (reset == Some("smallest")) {